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4<head>
5 <title>LLVM Programmer's Manual</title>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]6 <link rel="stylesheet" href="llvm.css" type="text/css">
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]7</head>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]8<body>
9
10<div class="doc_title">
11 LLVM Programmer's Manual
12</div>
13
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]14<ol>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]15 <li><a href="#introduction">Introduction</a></li>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]16 <li><a href="#general">General Information</a>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]17 <ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]18 <li><a href="#stl">The C++ Standard Template Library</a></li>
19<!--
20 <li>The <tt>-time-passes</tt> option</li>
21 <li>How to use the LLVM Makefile system</li>
22 <li>How to write a regression test</li>
Chris Lattner61db4652004-12-08 19:05:44 +0000[diff] [blame]23
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]24-->
Chris Lattner84b7f8d2003-08-01 22:20:59 +0000[diff] [blame]25 </ul>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]26 </li>
27 <li><a href="#apis">Important and useful LLVM APIs</a>
28 <ul>
29 <li><a href="#isa">The <tt>isa&lt;&gt;</tt>, <tt>cast&lt;&gt;</tt>
30and <tt>dyn_cast&lt;&gt;</tt> templates</a> </li>
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]31 <li><a href="#DEBUG">The <tt>DEBUG()</tt> macro and <tt>-debug</tt>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]32option</a>
33 <ul>
34 <li><a href="#DEBUG_TYPE">Fine grained debug info with <tt>DEBUG_TYPE</tt>
35and the <tt>-debug-only</tt> option</a> </li>
36 </ul>
37 </li>
Chris Lattner0be6fdf2006-12-19 21:46:21 +0000[diff] [blame]38 <li><a href="#Statistic">The <tt>Statistic</tt> class &amp; <tt>-stats</tt>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]39option</a></li>
40<!--
41 <li>The <tt>InstVisitor</tt> template
42 <li>The general graph API
43-->
Chris Lattnerf623a082005-10-17 01:36:23 +0000[diff] [blame]44 <li><a href="#ViewGraph">Viewing graphs while debugging code</a></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]45 </ul>
46 </li>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]47 <li><a href="#datastructure">Picking the Right Data Structure for a Task</a>
48 <ul>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame^]49 <li><a href="#ds_sequential">Sequential Containers (std::vector, std::list, etc)</a>
50 <ul>
51 <li><a href="#dss_fixedarrays">Fixed Size Arrays</a></li>
52 <li><a href="#dss_heaparrays">Heap Allocated Arrays</a></li>
53 <li><a href="#dss_smallvector">"llvm/ADT/SmallVector.h"</a></li>
54 <li><a href="#dss_vector">&lt;vector&gt;</a></li>
55 <li><a href="#dss_deque">&lt;deque&gt;</a></li>
56 <li><a href="#dss_list">&lt;list&gt;</a></li>
57 <li><a href="#dss_ilist">llvm/ADT/ilist</a></li>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]58 </ul></li>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame^]59 <li><a href="#ds_set">Set-Like Containers (std::set, SmallSet, SetVector, etc)</a>
60 <ul>
61 <li><a href="#dss_sortedvectorset">A sorted 'vector'</a></li>
62 <li><a href="#dss_smallset">"llvm/ADT/SmallSet.h"</a></li>
63 <li><a href="#dss_smallptrset">"llvm/ADT/SmallPtrSet.h"</a></li>
64 <li><a href="#dss_FoldingSet">"llvm/ADT/FoldingSet.h"</a></li>
65 <li><a href="#dss_set">&lt;set&gt;</a></li>
66 <li><a href="#dss_setvector">"llvm/ADT/SetVector.h"</a></li>
67 <li><a href="#dss_otherset">Other Options</a></li>
68 </ul></li>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]69 <li><a href="#ds_map">Map-Like Containers (std::map, DenseMap, etc)</a></li>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame^]70 </ul>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]71 </li>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]72 <li><a href="#common">Helpful Hints for Common Operations</a>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]73 <ul>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]74 <li><a href="#inspection">Basic Inspection and Traversal Routines</a>
75 <ul>
76 <li><a href="#iterate_function">Iterating over the <tt>BasicBlock</tt>s
77in a <tt>Function</tt></a> </li>
78 <li><a href="#iterate_basicblock">Iterating over the <tt>Instruction</tt>s
79in a <tt>BasicBlock</tt></a> </li>
80 <li><a href="#iterate_institer">Iterating over the <tt>Instruction</tt>s
81in a <tt>Function</tt></a> </li>
82 <li><a href="#iterate_convert">Turning an iterator into a
83class pointer</a> </li>
84 <li><a href="#iterate_complex">Finding call sites: a more
85complex example</a> </li>
86 <li><a href="#calls_and_invokes">Treating calls and invokes
87the same way</a> </li>
88 <li><a href="#iterate_chains">Iterating over def-use &amp;
89use-def chains</a> </li>
90 </ul>
91 </li>
92 <li><a href="#simplechanges">Making simple changes</a>
93 <ul>
94 <li><a href="#schanges_creating">Creating and inserting new
95 <tt>Instruction</tt>s</a> </li>
96 <li><a href="#schanges_deleting">Deleting <tt>Instruction</tt>s</a> </li>
97 <li><a href="#schanges_replacing">Replacing an <tt>Instruction</tt>
98with another <tt>Value</tt></a> </li>
99 </ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]100 </li>
Chris Lattnerae7f7592002-09-06 18:31:18 +0000[diff] [blame]101<!--
102 <li>Working with the Control Flow Graph
103 <ul>
104 <li>Accessing predecessors and successors of a <tt>BasicBlock</tt>
105 <li>
106 <li>
107 </ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]108-->
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]109 </ul>
110 </li>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]111
112 <li><a href="#advanced">Advanced Topics</a>
113 <ul>
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]114 <li><a href="#TypeResolve">LLVM Type Resolution</a>
115 <ul>
116 <li><a href="#BuildRecType">Basic Recursive Type Construction</a></li>
117 <li><a href="#refineAbstractTypeTo">The <tt>refineAbstractTypeTo</tt> method</a></li>
118 <li><a href="#PATypeHolder">The PATypeHolder Class</a></li>
119 <li><a href="#AbstractTypeUser">The AbstractTypeUser Class</a></li>
120 </ul></li>
121
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]122 <li><a href="#SymbolTable">The <tt>SymbolTable</tt> class </a></li>
123 </ul></li>
124
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]125 <li><a href="#coreclasses">The Core LLVM Class Hierarchy Reference</a>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]126 <ul>
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]127 <li><a href="#Type">The <tt>Type</tt> class</a> </li>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]128 <li><a href="#Value">The <tt>Value</tt> class</a>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]129 <ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]130 <li><a href="#User">The <tt>User</tt> class</a>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]131 <ul>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]132 <li><a href="#Instruction">The <tt>Instruction</tt> class</a>
133 <ul>
134 <li><a href="#GetElementPtrInst">The <tt>GetElementPtrInst</tt> class</a></li>
135 </ul>
136 </li>
137 <li><a href="#Module">The <tt>Module</tt> class</a></li>
138 <li><a href="#Constant">The <tt>Constant</tt> class</a>
139 <ul>
140 <li><a href="#GlobalValue">The <tt>GlobalValue</tt> class</a>
141 <ul>
142 <li><a href="#BasicBlock">The <tt>BasicBlock</tt>class</a></li>
143 <li><a href="#Function">The <tt>Function</tt> class</a></li>
144 <li><a href="#GlobalVariable">The <tt>GlobalVariable</tt> class</a></li>
145 </ul>
146 </li>
147 </ul>
148 </li>
Reid Spencer8b2da7a2004-07-18 13:10:31 +0000[diff] [blame]149 </ul>
150 </li>
Reid Spencer096603a2004-05-26 08:41:35 +0000[diff] [blame]151 <li><a href="#Argument">The <tt>Argument</tt> class</a></li>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]152 </ul>
153 </li>
154 </ul>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]155 </li>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]156</ol>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]157
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]158<div class="doc_author">
159 <p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a>,
Chris Lattner94c43592004-05-26 16:52:55 +0000[diff] [blame]160 <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a>,
161 <a href="mailto:jstanley@cs.uiuc.edu">Joel Stanley</a>, and
162 <a href="mailto:rspencer@x10sys.com">Reid Spencer</a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]163</div>
164
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]165<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]166<div class="doc_section">
167 <a name="introduction">Introduction </a>
168</div>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]169<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]170
171<div class="doc_text">
172
173<p>This document is meant to highlight some of the important classes and
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]174interfaces available in the LLVM source-base. This manual is not
175intended to explain what LLVM is, how it works, and what LLVM code looks
176like. It assumes that you know the basics of LLVM and are interested
177in writing transformations or otherwise analyzing or manipulating the
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]178code.</p>
179
180<p>This document should get you oriented so that you can find your
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]181way in the continuously growing source code that makes up the LLVM
182infrastructure. Note that this manual is not intended to serve as a
183replacement for reading the source code, so if you think there should be
184a method in one of these classes to do something, but it's not listed,
185check the source. Links to the <a href="/doxygen/">doxygen</a> sources
186are provided to make this as easy as possible.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]187
188<p>The first section of this document describes general information that is
189useful to know when working in the LLVM infrastructure, and the second describes
190the Core LLVM classes. In the future this manual will be extended with
191information describing how to use extension libraries, such as dominator
192information, CFG traversal routines, and useful utilities like the <tt><a
193href="/doxygen/InstVisitor_8h-source.html">InstVisitor</a></tt> template.</p>
194
195</div>
196
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]197<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]198<div class="doc_section">
199 <a name="general">General Information</a>
200</div>
201<!-- *********************************************************************** -->
202
203<div class="doc_text">
204
205<p>This section contains general information that is useful if you are working
206in the LLVM source-base, but that isn't specific to any particular API.</p>
207
208</div>
209
210<!-- ======================================================================= -->
211<div class="doc_subsection">
212 <a name="stl">The C++ Standard Template Library</a>
213</div>
214
215<div class="doc_text">
216
217<p>LLVM makes heavy use of the C++ Standard Template Library (STL),
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]218perhaps much more than you are used to, or have seen before. Because of
219this, you might want to do a little background reading in the
220techniques used and capabilities of the library. There are many good
221pages that discuss the STL, and several books on the subject that you
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]222can get, so it will not be discussed in this document.</p>
223
224<p>Here are some useful links:</p>
225
226<ol>
227
228<li><a href="http://www.dinkumware.com/refxcpp.html">Dinkumware C++ Library
229reference</a> - an excellent reference for the STL and other parts of the
230standard C++ library.</li>
231
232<li><a href="http://www.tempest-sw.com/cpp/">C++ In a Nutshell</a> - This is an
Tanya Lattner09cf73c2004-06-22 04:24:55 +0000[diff] [blame]233O'Reilly book in the making. It has a decent
234Standard Library
235Reference that rivals Dinkumware's, and is unfortunately no longer free since the book has been
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]236published.</li>
237
238<li><a href="http://www.parashift.com/c++-faq-lite/">C++ Frequently Asked
239Questions</a></li>
240
241<li><a href="http://www.sgi.com/tech/stl/">SGI's STL Programmer's Guide</a> -
242Contains a useful <a
243href="http://www.sgi.com/tech/stl/stl_introduction.html">Introduction to the
244STL</a>.</li>
245
246<li><a href="http://www.research.att.com/%7Ebs/C++.html">Bjarne Stroustrup's C++
247Page</a></li>
248
Tanya Lattner79445ba2004-12-08 18:34:56 +0000[diff] [blame]249<li><a href="http://64.78.49.204/">
Reid Spencer096603a2004-05-26 08:41:35 +0000[diff] [blame]250Bruce Eckel's Thinking in C++, 2nd ed. Volume 2 Revision 4.0 (even better, get
251the book).</a></li>
252
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]253</ol>
254
255<p>You are also encouraged to take a look at the <a
256href="CodingStandards.html">LLVM Coding Standards</a> guide which focuses on how
257to write maintainable code more than where to put your curly braces.</p>
258
259</div>
260
261<!-- ======================================================================= -->
262<div class="doc_subsection">
263 <a name="stl">Other useful references</a>
264</div>
265
266<div class="doc_text">
267
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]268<ol>
269<li><a href="http://www.psc.edu/%7Esemke/cvs_branches.html">CVS
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]270Branch and Tag Primer</a></li>
Misha Brukmana0f71e42004-06-18 18:39:00 +0000[diff] [blame]271<li><a href="http://www.fortran-2000.com/ArnaudRecipes/sharedlib.html">Using
272static and shared libraries across platforms</a></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]273</ol>
274
275</div>
276
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]277<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]278<div class="doc_section">
279 <a name="apis">Important and useful LLVM APIs</a>
280</div>
281<!-- *********************************************************************** -->
282
283<div class="doc_text">
284
285<p>Here we highlight some LLVM APIs that are generally useful and good to
286know about when writing transformations.</p>
287
288</div>
289
290<!-- ======================================================================= -->
291<div class="doc_subsection">
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]292 <a name="isa">The <tt>isa&lt;&gt;</tt>, <tt>cast&lt;&gt;</tt> and
293 <tt>dyn_cast&lt;&gt;</tt> templates</a>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]294</div>
295
296<div class="doc_text">
297
298<p>The LLVM source-base makes extensive use of a custom form of RTTI.
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]299These templates have many similarities to the C++ <tt>dynamic_cast&lt;&gt;</tt>
300operator, but they don't have some drawbacks (primarily stemming from
301the fact that <tt>dynamic_cast&lt;&gt;</tt> only works on classes that
302have a v-table). Because they are used so often, you must know what they
303do and how they work. All of these templates are defined in the <a
Chris Lattner695b78b2005-04-26 22:56:16 +0000[diff] [blame]304 href="/doxygen/Casting_8h-source.html"><tt>llvm/Support/Casting.h</tt></a>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]305file (note that you very rarely have to include this file directly).</p>
306
307<dl>
308 <dt><tt>isa&lt;&gt;</tt>: </dt>
309
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]310 <dd><p>The <tt>isa&lt;&gt;</tt> operator works exactly like the Java
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]311 "<tt>instanceof</tt>" operator. It returns true or false depending on whether
312 a reference or pointer points to an instance of the specified class. This can
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]313 be very useful for constraint checking of various sorts (example below).</p>
314 </dd>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]315
316 <dt><tt>cast&lt;&gt;</tt>: </dt>
317
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]318 <dd><p>The <tt>cast&lt;&gt;</tt> operator is a "checked cast" operation. It
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]319 converts a pointer or reference from a base class to a derived cast, causing
320 an assertion failure if it is not really an instance of the right type. This
321 should be used in cases where you have some information that makes you believe
322 that something is of the right type. An example of the <tt>isa&lt;&gt;</tt>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]323 and <tt>cast&lt;&gt;</tt> template is:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]324
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]325<div class="doc_code">
326<pre>
327static bool isLoopInvariant(const <a href="#Value">Value</a> *V, const Loop *L) {
328 if (isa&lt;<a href="#Constant">Constant</a>&gt;(V) || isa&lt;<a href="#Argument">Argument</a>&gt;(V) || isa&lt;<a href="#GlobalValue">GlobalValue</a>&gt;(V))
329 return true;
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]330
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]331 // <i>Otherwise, it must be an instruction...</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]332 return !L-&gt;contains(cast&lt;<a href="#Instruction">Instruction</a>&gt;(V)-&gt;getParent());
333}
334</pre>
335</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]336
337 <p>Note that you should <b>not</b> use an <tt>isa&lt;&gt;</tt> test followed
338 by a <tt>cast&lt;&gt;</tt>, for that use the <tt>dyn_cast&lt;&gt;</tt>
339 operator.</p>
340
341 </dd>
342
343 <dt><tt>dyn_cast&lt;&gt;</tt>:</dt>
344
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]345 <dd><p>The <tt>dyn_cast&lt;&gt;</tt> operator is a "checking cast" operation.
346 It checks to see if the operand is of the specified type, and if so, returns a
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]347 pointer to it (this operator does not work with references). If the operand is
348 not of the correct type, a null pointer is returned. Thus, this works very
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]349 much like the <tt>dynamic_cast&lt;&gt;</tt> operator in C++, and should be
350 used in the same circumstances. Typically, the <tt>dyn_cast&lt;&gt;</tt>
351 operator is used in an <tt>if</tt> statement or some other flow control
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]352 statement like this:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]353
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]354<div class="doc_code">
355<pre>
356if (<a href="#AllocationInst">AllocationInst</a> *AI = dyn_cast&lt;<a href="#AllocationInst">AllocationInst</a>&gt;(Val)) {
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]357 // <i>...</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]358}
359</pre>
360</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]361
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]362 <p>This form of the <tt>if</tt> statement effectively combines together a call
363 to <tt>isa&lt;&gt;</tt> and a call to <tt>cast&lt;&gt;</tt> into one
364 statement, which is very convenient.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]365
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]366 <p>Note that the <tt>dyn_cast&lt;&gt;</tt> operator, like C++'s
367 <tt>dynamic_cast&lt;&gt;</tt> or Java's <tt>instanceof</tt> operator, can be
368 abused. In particular, you should not use big chained <tt>if/then/else</tt>
369 blocks to check for lots of different variants of classes. If you find
370 yourself wanting to do this, it is much cleaner and more efficient to use the
371 <tt>InstVisitor</tt> class to dispatch over the instruction type directly.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]372
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]373 </dd>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]374
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]375 <dt><tt>cast_or_null&lt;&gt;</tt>: </dt>
376
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]377 <dd><p>The <tt>cast_or_null&lt;&gt;</tt> operator works just like the
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]378 <tt>cast&lt;&gt;</tt> operator, except that it allows for a null pointer as an
379 argument (which it then propagates). This can sometimes be useful, allowing
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]380 you to combine several null checks into one.</p></dd>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]381
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]382 <dt><tt>dyn_cast_or_null&lt;&gt;</tt>: </dt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]383
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]384 <dd><p>The <tt>dyn_cast_or_null&lt;&gt;</tt> operator works just like the
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]385 <tt>dyn_cast&lt;&gt;</tt> operator, except that it allows for a null pointer
386 as an argument (which it then propagates). This can sometimes be useful,
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]387 allowing you to combine several null checks into one.</p></dd>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]388
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]389</dl>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]390
391<p>These five templates can be used with any classes, whether they have a
392v-table or not. To add support for these templates, you simply need to add
393<tt>classof</tt> static methods to the class you are interested casting
394to. Describing this is currently outside the scope of this document, but there
395are lots of examples in the LLVM source base.</p>
396
397</div>
398
399<!-- ======================================================================= -->
400<div class="doc_subsection">
Misha Brukman2c122ce2005-11-01 21:12:49 +0000[diff] [blame]401 <a name="DEBUG">The <tt>DEBUG()</tt> macro and <tt>-debug</tt> option</a>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]402</div>
403
404<div class="doc_text">
405
406<p>Often when working on your pass you will put a bunch of debugging printouts
407and other code into your pass. After you get it working, you want to remove
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]408it, but you may need it again in the future (to work out new bugs that you run
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]409across).</p>
410
411<p> Naturally, because of this, you don't want to delete the debug printouts,
412but you don't want them to always be noisy. A standard compromise is to comment
413them out, allowing you to enable them if you need them in the future.</p>
414
Chris Lattner695b78b2005-04-26 22:56:16 +0000[diff] [blame]415<p>The "<tt><a href="/doxygen/Debug_8h-source.html">llvm/Support/Debug.h</a></tt>"
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]416file provides a macro named <tt>DEBUG()</tt> that is a much nicer solution to
417this problem. Basically, you can put arbitrary code into the argument of the
418<tt>DEBUG</tt> macro, and it is only executed if '<tt>opt</tt>' (or any other
419tool) is run with the '<tt>-debug</tt>' command line argument:</p>
420
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]421<div class="doc_code">
422<pre>
Bill Wendling832171c2006-12-07 20:04:42 +0000[diff] [blame]423DOUT &lt;&lt; "I am here!\n";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]424</pre>
425</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]426
427<p>Then you can run your pass like this:</p>
428
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]429<div class="doc_code">
430<pre>
431$ opt &lt; a.bc &gt; /dev/null -mypass
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]432<i>&lt;no output&gt;</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]433$ opt &lt; a.bc &gt; /dev/null -mypass -debug
434I am here!
435</pre>
436</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]437
438<p>Using the <tt>DEBUG()</tt> macro instead of a home-brewed solution allows you
439to not have to create "yet another" command line option for the debug output for
440your pass. Note that <tt>DEBUG()</tt> macros are disabled for optimized builds,
441so they do not cause a performance impact at all (for the same reason, they
442should also not contain side-effects!).</p>
443
444<p>One additional nice thing about the <tt>DEBUG()</tt> macro is that you can
445enable or disable it directly in gdb. Just use "<tt>set DebugFlag=0</tt>" or
446"<tt>set DebugFlag=1</tt>" from the gdb if the program is running. If the
447program hasn't been started yet, you can always just run it with
448<tt>-debug</tt>.</p>
449
450</div>
451
452<!-- _______________________________________________________________________ -->
453<div class="doc_subsubsection">
Chris Lattnerc9151082005-04-26 22:57:07 +0000[diff] [blame]454 <a name="DEBUG_TYPE">Fine grained debug info with <tt>DEBUG_TYPE</tt> and
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]455 the <tt>-debug-only</tt> option</a>
456</div>
457
458<div class="doc_text">
459
460<p>Sometimes you may find yourself in a situation where enabling <tt>-debug</tt>
461just turns on <b>too much</b> information (such as when working on the code
462generator). If you want to enable debug information with more fine-grained
463control, you define the <tt>DEBUG_TYPE</tt> macro and the <tt>-debug</tt> only
464option as follows:</p>
465
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]466<div class="doc_code">
467<pre>
Bill Wendling832171c2006-12-07 20:04:42 +0000[diff] [blame]468DOUT &lt;&lt; "No debug type\n";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]469#undef DEBUG_TYPE
470#define DEBUG_TYPE "foo"
Bill Wendling832171c2006-12-07 20:04:42 +0000[diff] [blame]471DOUT &lt;&lt; "'foo' debug type\n";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]472#undef DEBUG_TYPE
473#define DEBUG_TYPE "bar"
Bill Wendling832171c2006-12-07 20:04:42 +0000[diff] [blame]474DOUT &lt;&lt; "'bar' debug type\n";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]475#undef DEBUG_TYPE
476#define DEBUG_TYPE ""
Bill Wendling832171c2006-12-07 20:04:42 +0000[diff] [blame]477DOUT &lt;&lt; "No debug type (2)\n";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]478</pre>
479</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]480
481<p>Then you can run your pass like this:</p>
482
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]483<div class="doc_code">
484<pre>
485$ opt &lt; a.bc &gt; /dev/null -mypass
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]486<i>&lt;no output&gt;</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]487$ opt &lt; a.bc &gt; /dev/null -mypass -debug
488No debug type
489'foo' debug type
490'bar' debug type
491No debug type (2)
492$ opt &lt; a.bc &gt; /dev/null -mypass -debug-only=foo
493'foo' debug type
494$ opt &lt; a.bc &gt; /dev/null -mypass -debug-only=bar
495'bar' debug type
496</pre>
497</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]498
499<p>Of course, in practice, you should only set <tt>DEBUG_TYPE</tt> at the top of
500a file, to specify the debug type for the entire module (if you do this before
Chris Lattner695b78b2005-04-26 22:56:16 +0000[diff] [blame]501you <tt>#include "llvm/Support/Debug.h"</tt>, you don't have to insert the ugly
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]502<tt>#undef</tt>'s). Also, you should use names more meaningful than "foo" and
503"bar", because there is no system in place to ensure that names do not
504conflict. If two different modules use the same string, they will all be turned
505on when the name is specified. This allows, for example, all debug information
506for instruction scheduling to be enabled with <tt>-debug-type=InstrSched</tt>,
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]507even if the source lives in multiple files.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]508
509</div>
510
511<!-- ======================================================================= -->
512<div class="doc_subsection">
Chris Lattner0be6fdf2006-12-19 21:46:21 +0000[diff] [blame]513 <a name="Statistic">The <tt>Statistic</tt> class &amp; <tt>-stats</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]514 option</a>
515</div>
516
517<div class="doc_text">
518
519<p>The "<tt><a
Chris Lattner695b78b2005-04-26 22:56:16 +0000[diff] [blame]520href="/doxygen/Statistic_8h-source.html">llvm/ADT/Statistic.h</a></tt>" file
Chris Lattner0be6fdf2006-12-19 21:46:21 +0000[diff] [blame]521provides a class named <tt>Statistic</tt> that is used as a unified way to
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]522keep track of what the LLVM compiler is doing and how effective various
523optimizations are. It is useful to see what optimizations are contributing to
524making a particular program run faster.</p>
525
526<p>Often you may run your pass on some big program, and you're interested to see
527how many times it makes a certain transformation. Although you can do this with
528hand inspection, or some ad-hoc method, this is a real pain and not very useful
Chris Lattner0be6fdf2006-12-19 21:46:21 +0000[diff] [blame]529for big programs. Using the <tt>Statistic</tt> class makes it very easy to
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]530keep track of this information, and the calculated information is presented in a
531uniform manner with the rest of the passes being executed.</p>
532
533<p>There are many examples of <tt>Statistic</tt> uses, but the basics of using
534it are as follows:</p>
535
536<ol>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]537 <li><p>Define your statistic like this:</p>
538
539<div class="doc_code">
540<pre>
Chris Lattner0be6fdf2006-12-19 21:46:21 +0000[diff] [blame]541#define <a href="#DEBUG_TYPE">DEBUG_TYPE</a> "mypassname" <i>// This goes before any #includes.</i>
542STATISTIC(NumXForms, "The # of times I did stuff");
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]543</pre>
544</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]545
Chris Lattner0be6fdf2006-12-19 21:46:21 +0000[diff] [blame]546 <p>The <tt>STATISTIC</tt> macro defines a static variable, whose name is
547 specified by the first argument. The pass name is taken from the DEBUG_TYPE
548 macro, and the description is taken from the second argument. The variable
Reid Spencer06565dc2007-01-12 17:11:23 +0000[diff] [blame]549 defined ("NumXForms" in this case) acts like an unsigned integer.</p></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]550
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]551 <li><p>Whenever you make a transformation, bump the counter:</p>
552
553<div class="doc_code">
554<pre>
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]555++NumXForms; // <i>I did stuff!</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]556</pre>
557</div>
558
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]559 </li>
560 </ol>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]561
562 <p>That's all you have to do. To get '<tt>opt</tt>' to print out the
563 statistics gathered, use the '<tt>-stats</tt>' option:</p>
564
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]565<div class="doc_code">
566<pre>
567$ opt -stats -mypassname &lt; program.bc &gt; /dev/null
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]568<i>... statistics output ...</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]569</pre>
570</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]571
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]572 <p> When running <tt>gccas</tt> on a C file from the SPEC benchmark
573suite, it gives a report that looks like this:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]574
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]575<div class="doc_code">
576<pre>
577 7646 bytecodewriter - Number of normal instructions
578 725 bytecodewriter - Number of oversized instructions
579 129996 bytecodewriter - Number of bytecode bytes written
580 2817 raise - Number of insts DCEd or constprop'd
581 3213 raise - Number of cast-of-self removed
582 5046 raise - Number of expression trees converted
583 75 raise - Number of other getelementptr's formed
584 138 raise - Number of load/store peepholes
585 42 deadtypeelim - Number of unused typenames removed from symtab
586 392 funcresolve - Number of varargs functions resolved
587 27 globaldce - Number of global variables removed
588 2 adce - Number of basic blocks removed
589 134 cee - Number of branches revectored
590 49 cee - Number of setcc instruction eliminated
591 532 gcse - Number of loads removed
592 2919 gcse - Number of instructions removed
593 86 indvars - Number of canonical indvars added
594 87 indvars - Number of aux indvars removed
595 25 instcombine - Number of dead inst eliminate
596 434 instcombine - Number of insts combined
597 248 licm - Number of load insts hoisted
598 1298 licm - Number of insts hoisted to a loop pre-header
599 3 licm - Number of insts hoisted to multiple loop preds (bad, no loop pre-header)
600 75 mem2reg - Number of alloca's promoted
601 1444 cfgsimplify - Number of blocks simplified
602</pre>
603</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]604
605<p>Obviously, with so many optimizations, having a unified framework for this
606stuff is very nice. Making your pass fit well into the framework makes it more
607maintainable and useful.</p>
608
609</div>
610
Chris Lattnerf623a082005-10-17 01:36:23 +0000[diff] [blame]611<!-- ======================================================================= -->
612<div class="doc_subsection">
613 <a name="ViewGraph">Viewing graphs while debugging code</a>
614</div>
615
616<div class="doc_text">
617
618<p>Several of the important data structures in LLVM are graphs: for example
619CFGs made out of LLVM <a href="#BasicBlock">BasicBlock</a>s, CFGs made out of
620LLVM <a href="CodeGenerator.html#machinebasicblock">MachineBasicBlock</a>s, and
621<a href="CodeGenerator.html#selectiondag_intro">Instruction Selection
622DAGs</a>. In many cases, while debugging various parts of the compiler, it is
623nice to instantly visualize these graphs.</p>
624
625<p>LLVM provides several callbacks that are available in a debug build to do
626exactly that. If you call the <tt>Function::viewCFG()</tt> method, for example,
627the current LLVM tool will pop up a window containing the CFG for the function
628where each basic block is a node in the graph, and each node contains the
629instructions in the block. Similarly, there also exists
630<tt>Function::viewCFGOnly()</tt> (does not include the instructions), the
631<tt>MachineFunction::viewCFG()</tt> and <tt>MachineFunction::viewCFGOnly()</tt>,
632and the <tt>SelectionDAG::viewGraph()</tt> methods. Within GDB, for example,
Jim Laskey543a0ee2006-10-02 12:28:07 +0000[diff] [blame]633you can usually use something like <tt>call DAG.viewGraph()</tt> to pop
Chris Lattnerf623a082005-10-17 01:36:23 +0000[diff] [blame]634up a window. Alternatively, you can sprinkle calls to these functions in your
635code in places you want to debug.</p>
636
637<p>Getting this to work requires a small amount of configuration. On Unix
638systems with X11, install the <a href="http://www.graphviz.org">graphviz</a>
639toolkit, and make sure 'dot' and 'gv' are in your path. If you are running on
640Mac OS/X, download and install the Mac OS/X <a
641href="http://www.pixelglow.com/graphviz/">Graphviz program</a>, and add
642<tt>/Applications/Graphviz.app/Contents/MacOS/</tt> (or whereever you install
643it) to your path. Once in your system and path are set up, rerun the LLVM
644configure script and rebuild LLVM to enable this functionality.</p>
645
Jim Laskey543a0ee2006-10-02 12:28:07 +0000[diff] [blame]646<p><tt>SelectionDAG</tt> has been extended to make it easier to locate
647<i>interesting</i> nodes in large complex graphs. From gdb, if you
648<tt>call DAG.setGraphColor(<i>node</i>, "<i>color</i>")</tt>, then the
649next <tt>call DAG.viewGraph()</tt> would hilight the node in the
650specified color (choices of colors can be found at <a
Chris Lattner302da1e2007-02-03 03:05:57 +0000[diff] [blame]651href="http://www.graphviz.org/doc/info/colors.html">colors</a>.) More
Jim Laskey543a0ee2006-10-02 12:28:07 +0000[diff] [blame]652complex node attributes can be provided with <tt>call
653DAG.setGraphAttrs(<i>node</i>, "<i>attributes</i>")</tt> (choices can be
654found at <a href="http://www.graphviz.org/doc/info/attrs.html">Graph
655Attributes</a>.) If you want to restart and clear all the current graph
656attributes, then you can <tt>call DAG.clearGraphAttrs()</tt>. </p>
657
Chris Lattnerf623a082005-10-17 01:36:23 +0000[diff] [blame]658</div>
659
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]660<!-- *********************************************************************** -->
661<div class="doc_section">
662 <a name="datastructure">Picking the Right Data Structure for a Task</a>
663</div>
664<!-- *********************************************************************** -->
665
666<div class="doc_text">
667
668<p>LLVM has a plethora of datastructures in the <tt>llvm/ADT/</tt> directory,
669 and we commonly use STL datastructures. This section describes the tradeoffs
670 you should consider when you pick one.</p>
671
672<p>
673The first step is a choose your own adventure: do you want a sequential
674container, a set-like container, or a map-like container? The most important
675thing when choosing a container is the algorithmic properties of how you plan to
676access the container. Based on that, you should use:</p>
677
678<ul>
679<li>a <a href="#ds_map">map-like</a> container if you need efficient lookup
680 of an value based on another value. Map-like containers also support
681 efficient queries for containment (whether a key is in the map). Map-like
682 containers generally do not support efficient reverse mapping (values to
683 keys). If you need that, use two maps. Some map-like containers also
684 support efficient iteration through the keys in sorted order. Map-like
685 containers are the most expensive sort, only use them if you need one of
686 these capabilities.</li>
687
688<li>a <a href="#ds_set">set-like</a> container if you need to put a bunch of
689 stuff into a container that automatically eliminates duplicates. Some
690 set-like containers support efficient iteration through the elements in
691 sorted order. Set-like containers are more expensive than sequential
692 containers.
693</li>
694
695<li>a <a href="#ds_sequential">sequential</a> container provides
696 the most efficient way to add elements and keeps track of the order they are
697 added to the collection. They permit duplicates and support efficient
698 iteration, but do not support efficient lookup based on a key.
699</li>
700
701</ul>
702
703<p>
704Once the proper catagory of container is determined, you can fine tune the
705memory use, constant factors, and cache behaviors of access by intelligently
706picking a member of the catagory. Note that constant factors and cache behavior
707can be a big deal. If you have a vector that usually only contains a few
708elements (but could contain many), for example, it's much better to use
709<a href="#dss_smallvector">SmallVector</a> than <a href="#dss_vector">vector</a>
710. Doing so avoids (relatively) expensive malloc/free calls, which dwarf the
711cost of adding the elements to the container. </p>
712
713</div>
714
715<!-- ======================================================================= -->
716<div class="doc_subsection">
717 <a name="ds_sequential">Sequential Containers (std::vector, std::list, etc)</a>
718</div>
719
720<div class="doc_text">
721There are a variety of sequential containers available for you, based on your
722needs. Pick the first in this section that will do what you want.
723</div>
724
725<!-- _______________________________________________________________________ -->
726<div class="doc_subsubsection">
727 <a name="dss_fixedarrays">Fixed Size Arrays</a>
728</div>
729
730<div class="doc_text">
731<p>Fixed size arrays are very simple and very fast. They are good if you know
732exactly how many elements you have, or you have a (low) upper bound on how many
733you have.</p>
734</div>
735
736<!-- _______________________________________________________________________ -->
737<div class="doc_subsubsection">
738 <a name="dss_heaparrays">Heap Allocated Arrays</a>
739</div>
740
741<div class="doc_text">
742<p>Heap allocated arrays (new[] + delete[]) are also simple. They are good if
743the number of elements is variable, if you know how many elements you will need
744before the array is allocated, and if the array is usually large (if not,
745consider a <a href="#dss_smallvector">SmallVector</a>). The cost of a heap
746allocated array is the cost of the new/delete (aka malloc/free). Also note that
747if you are allocating an array of a type with a constructor, the constructor and
748destructors will be run for every element in the array (resizable vectors only
749construct those elements actually used).</p>
750</div>
751
752<!-- _______________________________________________________________________ -->
753<div class="doc_subsubsection">
754 <a name="dss_smallvector">"llvm/ADT/SmallVector.h"</a>
755</div>
756
757<div class="doc_text">
758<p><tt>SmallVector&lt;Type, N&gt;</tt> is a simple class that looks and smells
759just like <tt>vector&lt;Type&gt;</tt>:
760it supports efficient iteration, lays out elements in memory order (so you can
761do pointer arithmetic between elements), supports efficient push_back/pop_back
762operations, supports efficient random access to its elements, etc.</p>
763
764<p>The advantage of SmallVector is that it allocates space for
765some number of elements (N) <b>in the object itself</b>. Because of this, if
766the SmallVector is dynamically smaller than N, no malloc is performed. This can
767be a big win in cases where the malloc/free call is far more expensive than the
768code that fiddles around with the elements.</p>
769
770<p>This is good for vectors that are "usually small" (e.g. the number of
771predecessors/successors of a block is usually less than 8). On the other hand,
772this makes the size of the SmallVector itself large, so you don't want to
773allocate lots of them (doing so will waste a lot of space). As such,
774SmallVectors are most useful when on the stack.</p>
775
776<p>SmallVector also provides a nice portable and efficient replacement for
777<tt>alloca</tt>.</p>
778
779</div>
780
781<!-- _______________________________________________________________________ -->
782<div class="doc_subsubsection">
783 <a name="dss_vector">&lt;vector&gt;</a>
784</div>
785
786<div class="doc_text">
787<p>
788std::vector is well loved and respected. It is useful when SmallVector isn't:
789when the size of the vector is often large (thus the small optimization will
790rarely be a benefit) or if you will be allocating many instances of the vector
791itself (which would waste space for elements that aren't in the container).
792vector is also useful when interfacing with code that expects vectors :).
793</p>
794</div>
795
796<!-- _______________________________________________________________________ -->
797<div class="doc_subsubsection">
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame^]798 <a name="dss_deque">&lt;deque&gt;</a>
799</div>
800
801<div class="doc_text">
802<p>std::deque is, in some senses, a generalized version of std::vector. Like
803std::vector, it provides constant time random access and other similar
804properties, but it also provides efficient access to the front of the list. It
805does not guarantee continuity of elements within memory.</p>
806
807<p>In exchange for this extra flexibility, std::deque has significantly higher
808constant factor costs than std::vector. If possible, use std::vector or
809something cheaper.</p>
810</div>
811
812<!-- _______________________________________________________________________ -->
813<div class="doc_subsubsection">
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]814 <a name="dss_list">&lt;list&gt;</a>
815</div>
816
817<div class="doc_text">
818<p>std::list is an extremely inefficient class that is rarely useful.
819It performs a heap allocation for every element inserted into it, thus having an
820extremely high constant factor, particularly for small data types. std::list
821also only supports bidirectional iteration, not random access iteration.</p>
822
823<p>In exchange for this high cost, std::list supports efficient access to both
824ends of the list (like std::deque, but unlike std::vector or SmallVector). In
825addition, the iterator invalidation characteristics of std::list are stronger
826than that of a vector class: inserting or removing an element into the list does
827not invalidate iterator or pointers to other elements in the list.</p>
828</div>
829
830<!-- _______________________________________________________________________ -->
831<div class="doc_subsubsection">
832 <a name="dss_ilist">llvm/ADT/ilist</a>
833</div>
834
835<div class="doc_text">
836<p><tt>ilist&lt;T&gt;</tt> implements an 'intrusive' doubly-linked list. It is
837intrusive, because it requires the element to store and provide access to the
838prev/next pointers for the list.</p>
839
840<p>ilist has the same drawbacks as std::list, and additionally requires an
841ilist_traits implementation for the element type, but it provides some novel
842characteristics. In particular, it can efficiently store polymorphic objects,
843the traits class is informed when an element is inserted or removed from the
844list, and ilists are guaranteed to support a constant-time splice operation.
845</p>
846
847<p>These properties are exactly what we want for things like Instructions and
848basic blocks, which is why these are implemented with ilists.</p>
849</div>
850
851<!-- _______________________________________________________________________ -->
852<div class="doc_subsubsection">
853 <a name="dss_other">Other options</a>
854</div>
855
856<div class="doc_text">
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame^]857<p>Other STL containers are available, such as std::string.</p>
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]858
859<p>There are also various STL adapter classes such as std::queue,
860std::priority_queue, std::stack, etc. These provide simplified access to an
861underlying container but don't affect the cost of the container itself.</p>
862
863</div>
864
865
866<!-- ======================================================================= -->
867<div class="doc_subsection">
868 <a name="ds_set">Set-Like Containers (std::set, SmallSet, SetVector, etc)</a>
869</div>
870
871<div class="doc_text">
872
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame^]873<p>Set-like containers are useful when you need to canonicalize multiple values
874into a single representation. There are several different choices for how to do
875this, providing various trade-offs.</p>
876
877</div>
878
879
880<!-- _______________________________________________________________________ -->
881<div class="doc_subsubsection">
882 <a name="dss_sortedvectorset">A sorted 'vector'</a>
883</div>
884
885<div class="doc_text">
886
887<p>If you intend to insert a lot of elements, then do a lot of queries, one
888great approach is to use a vector (or other sequential container), and then use
889std::sort+std::unique to remove duplicates. This approach works really well if
890your usage pattern has these two distinct phases (insert then query), and,
891coupled with a good choice of <a href="#ds_sequential">sequential container</a>
892can provide the several nice properties: the result data is contiguous in memory
893(good for cache locality), has few allocations, is easy to address (iterators in
894the final vector are just indices or pointers), and can be efficiently queried
895with a standard binary search.</p>
896
897</div>
898
899<!-- _______________________________________________________________________ -->
900<div class="doc_subsubsection">
901 <a name="dss_smallset">"llvm/ADT/SmallSet.h"</a>
902</div>
903
904<div class="doc_text">
905
906<p>If you have a set-like datastructure that is usually small and whose elements
907are reasonably small, a <tt>SmallSet&lt;Type, N&gt; is a good choice. This set
908has space for N elements in place (thus, if the set is dynamically smaller than
909N, no malloc traffic is required) and access them with a simple linear search.
910When the set grows beyond 'N', it allocates a more expensive representation that
911guarantees efficient access (for most types, it falls back to std::set, but for
912pointers it uses something far better, see <a
913href="#dss_smallptrset">SmallPtrSet</a>).</p>
914
915<p>The magic of this class is that it handles small sets extremely efficiently,
916but gracefully handles extremely large sets without loss of efficiency. The
917drawback is that the interface is quite small: it supports insertion, queries
918and erasing, but does not support iteration.</p>
919
920</div>
921
922<!-- _______________________________________________________________________ -->
923<div class="doc_subsubsection">
924 <a name="dss_smallptrset">"llvm/ADT/SmallPtrSet.h"</a>
925</div>
926
927<div class="doc_text">
928
929<p>SmallPtrSet has all the advantages of SmallSet (and a SmallSet of pointers is
930transparently implemented with a SmallPtrSet), but also suports iterators. If
931more than 'N' allocations are performed, a single quadratically
932probed hash table is allocated and grows as needed, providing extremely
933efficient access (constant time insertion/deleting/queries with low constant
934factors) and is very stingy with malloc traffic.</p>
935
936<p>Note that, unlike std::set, the iterators of SmallPtrSet are invalidated
937whenever an insertion occurs. Also, the values visited by the iterators are not
938visited in sorted order.</p>
939
940</div>
941
942<!-- _______________________________________________________________________ -->
943<div class="doc_subsubsection">
944 <a name="dss_FoldingSet">"llvm/ADT/FoldingSet.h"</a>
945</div>
946
947<div class="doc_text">
948
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]949<p>
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame^]950FoldingSet is an aggregate class that is really good at uniquing
951expensive-to-create or polymorphic objects. It is a combination of a chained
952hash table with intrusive links (uniqued objects are required to inherit from
953FoldingSetNode) that uses SmallVector as part of its ID process.</p>
954
955<p>Consider a case where you want to implement a "getorcreate_foo" method for
956a complex object (for example, a node in the code generator). The client has a
957description of *what* it wants to generate (it knows the opcode and all the
958operands), but we don't want to 'new' a node, then try inserting it into a set
959only to find out it already exists (at which point we would have to delete it
960and return the node that already exists).
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]961</p>
962
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame^]963<p>To support this style of client, FoldingSet perform a query with a
964FoldingSetNodeID (which wraps SmallVector) that can be used to describe the
965element that we want to query for. The query either returns the element
966matching the ID or it returns an opaque ID that indicates where insertion should
967take place.</p>
968
969<p>Because FoldingSet uses intrusive links, it can support polymorphic objects
970in the set (for example, you can have SDNode instances mixed with LoadSDNodes).
971Because the elements are individually allocated, pointers to the elements are
972stable: inserting or removing elements does not invalidate any pointers to other
973elements.
974</p>
975
976</div>
977
978<!-- _______________________________________________________________________ -->
979<div class="doc_subsubsection">
980 <a name="dss_set">&lt;set&gt;</a>
981</div>
982
983<div class="doc_text">
984
985<p>std::set is a reasonable all-around set class, which is good at many things
986but great at nothing. std::set use a allocates memory for every single element
987inserted (thus it is very malloc intensive) and typically stores three pointers
988with every element (thus adding a large amount of per-element space overhead).
989It offers guaranteed log(n) performance, which is not particularly fast.
990</p>
991
992<p>The advantages of std::set is that its iterators are stable (deleting or
993inserting an element from the set does not affect iterators or pointers to other
994elements) and that iteration over the set is guaranteed to be in sorted order.
995If the elements in the set are large, then the relative overhead of the pointers
996and malloc traffic is not a big deal, but if the elements of the set are small,
997std::set is almost never a good choice.</p>
998
999</div>
1000
1001<!-- _______________________________________________________________________ -->
1002<div class="doc_subsubsection">
1003 <a name="dss_setvector">"llvm/ADT/SetVector.h"</a>
1004</div>
1005
1006<div class="doc_text">
1007<p>LLVM's SetVector&lt;Type&gt; is actually a combination of a set along with
1008a <a href="#ds_sequential">Sequential Container</a>. The important property
1009that this provides is efficient insertion with uniquing (duplicate elements are
1010ignored) with iteration support. It implements this by inserting elements into
1011both a set-like container and the sequential container, using the set-like
1012container for uniquing and the sequential container for iteration.
1013</p>
1014
1015<p>The difference between SetVector and other sets is that the order of
1016iteration is guaranteed to match the order of insertion into the SetVector.
1017This property is really important for things like sets of pointers. Because
1018pointer values are non-deterministic (e.g. vary across runs of the program on
1019different machines), iterating over the pointers in a std::set or other set will
1020not be in a well-defined order.</p>
1021
1022<p>
1023The drawback of SetVector is that it requires twice as much space as a normal
1024set and has the sum of constant factors from the set-like container and the
1025sequential container that it uses. Use it *only* if you need to iterate over
1026the elements in a deterministic order. SetVector is also expensive to delete
1027elements out of (linear time).
1028</p>
1029
1030</div>
1031
1032<!-- _______________________________________________________________________ -->
1033<div class="doc_subsubsection">
1034 <a name="dss_otherset">Other Options</a>
1035</div>
1036
1037<div class="doc_text">
1038
1039<p>
1040The STL provides several other options, such as std::multiset and the various
1041"hash_set" like containers (whether from C++TR1 or from the SGI library).</p>
1042
1043<p>std::multiset is useful if you're not interested in elimination of
1044duplicates, but has all the drawbacks of std::set. A sorted vector or some
1045other approach is almost always better.</p>
1046
1047<p>The various hash_set implementations (exposed portably by
1048"llvm/ADT/hash_set") is a standard chained hashtable. This algorithm is malloc
1049intensive like std::set (performing an allocation for each element inserted,
1050thus having really high constant factors) but (usually) provides O(1)
1051insertion/deletion of elements. This can be useful if your elements are large
1052(thus making the constant-factor cost relatively low). Element iteration does
1053not visit elements in a useful order.</p>
1054
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]1055</div>
1056
1057<!-- ======================================================================= -->
1058<div class="doc_subsection">
1059 <a name="ds_map">Map-Like Containers (std::map, DenseMap, etc)</a>
1060</div>
1061
1062<div class="doc_text">
1063sorted vector
1064std::map
1065DenseMap
Chris Lattner74c4ca12007-02-03 07:59:07 +0000[diff] [blame^]1066UniqueVector
Chris Lattner098129a2007-02-03 03:04:03 +0000[diff] [blame]1067IndexedMap
1068hash_map
1069CStringMap
1070</div>
1071
Chris Lattnerf623a082005-10-17 01:36:23 +0000[diff] [blame]1072
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1073<!-- *********************************************************************** -->
1074<div class="doc_section">
1075 <a name="common">Helpful Hints for Common Operations</a>
1076</div>
1077<!-- *********************************************************************** -->
1078
1079<div class="doc_text">
1080
1081<p>This section describes how to perform some very simple transformations of
1082LLVM code. This is meant to give examples of common idioms used, showing the
1083practical side of LLVM transformations. <p> Because this is a "how-to" section,
1084you should also read about the main classes that you will be working with. The
1085<a href="#coreclasses">Core LLVM Class Hierarchy Reference</a> contains details
1086and descriptions of the main classes that you should know about.</p>
1087
1088</div>
1089
1090<!-- NOTE: this section should be heavy on example code -->
1091<!-- ======================================================================= -->
1092<div class="doc_subsection">
1093 <a name="inspection">Basic Inspection and Traversal Routines</a>
1094</div>
1095
1096<div class="doc_text">
1097
1098<p>The LLVM compiler infrastructure have many different data structures that may
1099be traversed. Following the example of the C++ standard template library, the
1100techniques used to traverse these various data structures are all basically the
1101same. For a enumerable sequence of values, the <tt>XXXbegin()</tt> function (or
1102method) returns an iterator to the start of the sequence, the <tt>XXXend()</tt>
1103function returns an iterator pointing to one past the last valid element of the
1104sequence, and there is some <tt>XXXiterator</tt> data type that is common
1105between the two operations.</p>
1106
1107<p>Because the pattern for iteration is common across many different aspects of
1108the program representation, the standard template library algorithms may be used
1109on them, and it is easier to remember how to iterate. First we show a few common
1110examples of the data structures that need to be traversed. Other data
1111structures are traversed in very similar ways.</p>
1112
1113</div>
1114
1115<!-- _______________________________________________________________________ -->
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]1116<div class="doc_subsubsection">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1117 <a name="iterate_function">Iterating over the </a><a
1118 href="#BasicBlock"><tt>BasicBlock</tt></a>s in a <a
1119 href="#Function"><tt>Function</tt></a>
1120</div>
1121
1122<div class="doc_text">
1123
1124<p>It's quite common to have a <tt>Function</tt> instance that you'd like to
1125transform in some way; in particular, you'd like to manipulate its
1126<tt>BasicBlock</tt>s. To facilitate this, you'll need to iterate over all of
1127the <tt>BasicBlock</tt>s that constitute the <tt>Function</tt>. The following is
1128an example that prints the name of a <tt>BasicBlock</tt> and the number of
1129<tt>Instruction</tt>s it contains:</p>
1130
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1131<div class="doc_code">
1132<pre>
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1133// <i>func is a pointer to a Function instance</i>
1134for (Function::iterator i = func-&gt;begin(), e = func-&gt;end(); i != e; ++i)
1135 // <i>Print out the name of the basic block if it has one, and then the</i>
1136 // <i>number of instructions that it contains</i>
Bill Wendling832171c2006-12-07 20:04:42 +0000[diff] [blame]1137 llvm::cerr &lt;&lt; "Basic block (name=" &lt;&lt; i-&gt;getName() &lt;&lt; ") has "
1138 &lt;&lt; i-&gt;size() &lt;&lt; " instructions.\n";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1139</pre>
1140</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1141
1142<p>Note that i can be used as if it were a pointer for the purposes of
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]1143invoking member functions of the <tt>Instruction</tt> class. This is
1144because the indirection operator is overloaded for the iterator
Chris Lattner7496ec52003-08-05 22:54:23 +0000[diff] [blame]1145classes. In the above code, the expression <tt>i-&gt;size()</tt> is
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1146exactly equivalent to <tt>(*i).size()</tt> just like you'd expect.</p>
1147
1148</div>
1149
1150<!-- _______________________________________________________________________ -->
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]1151<div class="doc_subsubsection">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1152 <a name="iterate_basicblock">Iterating over the </a><a
1153 href="#Instruction"><tt>Instruction</tt></a>s in a <a
1154 href="#BasicBlock"><tt>BasicBlock</tt></a>
1155</div>
1156
1157<div class="doc_text">
1158
1159<p>Just like when dealing with <tt>BasicBlock</tt>s in <tt>Function</tt>s, it's
1160easy to iterate over the individual instructions that make up
1161<tt>BasicBlock</tt>s. Here's a code snippet that prints out each instruction in
1162a <tt>BasicBlock</tt>:</p>
1163
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1164<div class="doc_code">
Chris Lattner55c04612005-03-06 06:00:13 +0000[diff] [blame]1165<pre>
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1166// <i>blk is a pointer to a BasicBlock instance</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1167for (BasicBlock::iterator i = blk-&gt;begin(), e = blk-&gt;end(); i != e; ++i)
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1168 // <i>The next statement works since operator&lt;&lt;(ostream&amp;,...)</i>
1169 // <i>is overloaded for Instruction&amp;</i>
Bill Wendling832171c2006-12-07 20:04:42 +0000[diff] [blame]1170 llvm::cerr &lt;&lt; *i &lt;&lt; "\n";
Chris Lattner55c04612005-03-06 06:00:13 +0000[diff] [blame]1171</pre>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1172</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1173
1174<p>However, this isn't really the best way to print out the contents of a
1175<tt>BasicBlock</tt>! Since the ostream operators are overloaded for virtually
1176anything you'll care about, you could have just invoked the print routine on the
Bill Wendling832171c2006-12-07 20:04:42 +0000[diff] [blame]1177basic block itself: <tt>llvm::cerr &lt;&lt; *blk &lt;&lt; "\n";</tt>.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1178
1179</div>
1180
1181<!-- _______________________________________________________________________ -->
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]1182<div class="doc_subsubsection">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1183 <a name="iterate_institer">Iterating over the </a><a
1184 href="#Instruction"><tt>Instruction</tt></a>s in a <a
1185 href="#Function"><tt>Function</tt></a>
1186</div>
1187
1188<div class="doc_text">
1189
1190<p>If you're finding that you commonly iterate over a <tt>Function</tt>'s
1191<tt>BasicBlock</tt>s and then that <tt>BasicBlock</tt>'s <tt>Instruction</tt>s,
1192<tt>InstIterator</tt> should be used instead. You'll need to include <a
1193href="/doxygen/InstIterator_8h-source.html"><tt>llvm/Support/InstIterator.h</tt></a>,
1194and then instantiate <tt>InstIterator</tt>s explicitly in your code. Here's a
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]1195small example that shows how to dump all instructions in a function to the standard error stream:<p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1196
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1197<div class="doc_code">
1198<pre>
1199#include "<a href="/doxygen/InstIterator_8h-source.html">llvm/Support/InstIterator.h</a>"
1200
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1201// <i>F is a ptr to a Function instance</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1202for (inst_iterator i = inst_begin(F), e = inst_end(F); i != e; ++i)
Bill Wendling832171c2006-12-07 20:04:42 +0000[diff] [blame]1203 llvm::cerr &lt;&lt; *i &lt;&lt; "\n";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1204</pre>
1205</div>
1206
1207<p>Easy, isn't it? You can also use <tt>InstIterator</tt>s to fill a
Joel Stanleye7be6502002-09-09 15:50:33 +0000[diff] [blame]1208worklist with its initial contents. For example, if you wanted to
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1209initialize a worklist to contain all instructions in a <tt>Function</tt>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1210F, all you would need to do is something like:</p>
1211
1212<div class="doc_code">
1213<pre>
1214std::set&lt;Instruction*&gt; worklist;
1215worklist.insert(inst_begin(F), inst_end(F));
1216</pre>
1217</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1218
1219<p>The STL set <tt>worklist</tt> would now contain all instructions in the
1220<tt>Function</tt> pointed to by F.</p>
1221
1222</div>
1223
1224<!-- _______________________________________________________________________ -->
1225<div class="doc_subsubsection">
1226 <a name="iterate_convert">Turning an iterator into a class pointer (and
1227 vice-versa)</a>
1228</div>
1229
1230<div class="doc_text">
1231
1232<p>Sometimes, it'll be useful to grab a reference (or pointer) to a class
Joel Stanley9b96c442002-09-06 21:55:13 +0000[diff] [blame]1233instance when all you've got at hand is an iterator. Well, extracting
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]1234a reference or a pointer from an iterator is very straight-forward.
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1235Assuming that <tt>i</tt> is a <tt>BasicBlock::iterator</tt> and <tt>j</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1236is a <tt>BasicBlock::const_iterator</tt>:</p>
1237
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1238<div class="doc_code">
1239<pre>
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1240Instruction&amp; inst = *i; // <i>Grab reference to instruction reference</i>
1241Instruction* pinst = &amp;*i; // <i>Grab pointer to instruction reference</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1242const Instruction&amp; inst = *j;
1243</pre>
1244</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1245
1246<p>However, the iterators you'll be working with in the LLVM framework are
1247special: they will automatically convert to a ptr-to-instance type whenever they
1248need to. Instead of dereferencing the iterator and then taking the address of
1249the result, you can simply assign the iterator to the proper pointer type and
1250you get the dereference and address-of operation as a result of the assignment
1251(behind the scenes, this is a result of overloading casting mechanisms). Thus
1252the last line of the last example,</p>
1253
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1254<div class="doc_code">
1255<pre>
1256Instruction* pinst = &amp;*i;
1257</pre>
1258</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1259
1260<p>is semantically equivalent to</p>
1261
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1262<div class="doc_code">
1263<pre>
1264Instruction* pinst = i;
1265</pre>
1266</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1267
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]1268<p>It's also possible to turn a class pointer into the corresponding iterator,
1269and this is a constant time operation (very efficient). The following code
1270snippet illustrates use of the conversion constructors provided by LLVM
1271iterators. By using these, you can explicitly grab the iterator of something
1272without actually obtaining it via iteration over some structure:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1273
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1274<div class="doc_code">
1275<pre>
1276void printNextInstruction(Instruction* inst) {
1277 BasicBlock::iterator it(inst);
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1278 ++it; // <i>After this line, it refers to the instruction after *inst</i>
Bill Wendling832171c2006-12-07 20:04:42 +0000[diff] [blame]1279 if (it != inst-&gt;getParent()-&gt;end()) llvm::cerr &lt;&lt; *it &lt;&lt; "\n";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1280}
1281</pre>
1282</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1283
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1284</div>
1285
1286<!--_______________________________________________________________________-->
1287<div class="doc_subsubsection">
1288 <a name="iterate_complex">Finding call sites: a slightly more complex
1289 example</a>
1290</div>
1291
1292<div class="doc_text">
1293
1294<p>Say that you're writing a FunctionPass and would like to count all the
1295locations in the entire module (that is, across every <tt>Function</tt>) where a
1296certain function (i.e., some <tt>Function</tt>*) is already in scope. As you'll
1297learn later, you may want to use an <tt>InstVisitor</tt> to accomplish this in a
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]1298much more straight-forward manner, but this example will allow us to explore how
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1299you'd do it if you didn't have <tt>InstVisitor</tt> around. In pseudocode, this
1300is what we want to do:</p>
1301
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1302<div class="doc_code">
1303<pre>
1304initialize callCounter to zero
1305for each Function f in the Module
1306 for each BasicBlock b in f
1307 for each Instruction i in b
1308 if (i is a CallInst and calls the given function)
1309 increment callCounter
1310</pre>
1311</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1312
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1313<p>And the actual code is (remember, because we're writing a
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1314<tt>FunctionPass</tt>, our <tt>FunctionPass</tt>-derived class simply has to
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1315override the <tt>runOnFunction</tt> method):</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1316
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1317<div class="doc_code">
1318<pre>
1319Function* targetFunc = ...;
1320
1321class OurFunctionPass : public FunctionPass {
1322 public:
1323 OurFunctionPass(): callCounter(0) { }
1324
1325 virtual runOnFunction(Function&amp; F) {
1326 for (Function::iterator b = F.begin(), be = F.end(); b != be; ++b) {
1327 for (BasicBlock::iterator i = b-&gt;begin(); ie = b-&gt;end(); i != ie; ++i) {
1328 if (<a href="#CallInst">CallInst</a>* callInst = <a href="#isa">dyn_cast</a>&lt;<a
1329 href="#CallInst">CallInst</a>&gt;(&amp;*i)) {
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1330 // <i>We know we've encountered a call instruction, so we</i>
1331 // <i>need to determine if it's a call to the</i>
1332 // <i>function pointed to by m_func or not</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1333
1334 if (callInst-&gt;getCalledFunction() == targetFunc)
1335 ++callCounter;
1336 }
1337 }
1338 }
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1339 }
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1340
1341 private:
1342 unsigned callCounter;
1343};
1344</pre>
1345</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1346
1347</div>
1348
Brian Gaekef1972c62003-11-07 19:25:45 +0000[diff] [blame]1349<!--_______________________________________________________________________-->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1350<div class="doc_subsubsection">
1351 <a name="calls_and_invokes">Treating calls and invokes the same way</a>
1352</div>
1353
1354<div class="doc_text">
1355
1356<p>You may have noticed that the previous example was a bit oversimplified in
1357that it did not deal with call sites generated by 'invoke' instructions. In
1358this, and in other situations, you may find that you want to treat
1359<tt>CallInst</tt>s and <tt>InvokeInst</tt>s the same way, even though their
1360most-specific common base class is <tt>Instruction</tt>, which includes lots of
1361less closely-related things. For these cases, LLVM provides a handy wrapper
1362class called <a
Reid Spencer05fe4b02006-03-14 05:39:39 +0000[diff] [blame]1363href="http://llvm.org/doxygen/classllvm_1_1CallSite.html"><tt>CallSite</tt></a>.
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]1364It is essentially a wrapper around an <tt>Instruction</tt> pointer, with some
1365methods that provide functionality common to <tt>CallInst</tt>s and
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1366<tt>InvokeInst</tt>s.</p>
1367
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]1368<p>This class has "value semantics": it should be passed by value, not by
1369reference and it should not be dynamically allocated or deallocated using
1370<tt>operator new</tt> or <tt>operator delete</tt>. It is efficiently copyable,
1371assignable and constructable, with costs equivalents to that of a bare pointer.
1372If you look at its definition, it has only a single pointer member.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1373
1374</div>
1375
Chris Lattner1a3105b2002-09-09 05:49:39 +0000[diff] [blame]1376<!--_______________________________________________________________________-->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1377<div class="doc_subsubsection">
1378 <a name="iterate_chains">Iterating over def-use &amp; use-def chains</a>
1379</div>
1380
1381<div class="doc_text">
1382
1383<p>Frequently, we might have an instance of the <a
Chris Lattner00815172007-01-04 22:01:45 +0000[diff] [blame]1384href="/doxygen/classllvm_1_1Value.html">Value Class</a> and we want to
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]1385determine which <tt>User</tt>s use the <tt>Value</tt>. The list of all
1386<tt>User</tt>s of a particular <tt>Value</tt> is called a <i>def-use</i> chain.
1387For example, let's say we have a <tt>Function*</tt> named <tt>F</tt> to a
1388particular function <tt>foo</tt>. Finding all of the instructions that
1389<i>use</i> <tt>foo</tt> is as simple as iterating over the <i>def-use</i> chain
1390of <tt>F</tt>:</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1391
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1392<div class="doc_code">
1393<pre>
1394Function* F = ...;
1395
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1396for (Value::use_iterator i = F-&gt;use_begin(), e = F-&gt;use_end(); i != e; ++i)
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1397 if (Instruction *Inst = dyn_cast&lt;Instruction&gt;(*i)) {
Bill Wendling832171c2006-12-07 20:04:42 +0000[diff] [blame]1398 llvm::cerr &lt;&lt; "F is used in instruction:\n";
1399 llvm::cerr &lt;&lt; *Inst &lt;&lt; "\n";
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1400 }
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1401</pre>
1402</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1403
1404<p>Alternately, it's common to have an instance of the <a
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]1405href="/doxygen/classllvm_1_1User.html">User Class</a> and need to know what
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1406<tt>Value</tt>s are used by it. The list of all <tt>Value</tt>s used by a
1407<tt>User</tt> is known as a <i>use-def</i> chain. Instances of class
1408<tt>Instruction</tt> are common <tt>User</tt>s, so we might want to iterate over
1409all of the values that a particular instruction uses (that is, the operands of
1410the particular <tt>Instruction</tt>):</p>
1411
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1412<div class="doc_code">
1413<pre>
1414Instruction* pi = ...;
1415
1416for (User::op_iterator i = pi-&gt;op_begin(), e = pi-&gt;op_end(); i != e; ++i) {
1417 Value* v = *i;
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1418 // <i>...</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1419}
1420</pre>
1421</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1422
Chris Lattner1a3105b2002-09-09 05:49:39 +0000[diff] [blame]1423<!--
1424 def-use chains ("finding all users of"): Value::use_begin/use_end
1425 use-def chains ("finding all values used"): User::op_begin/op_end [op=operand]
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1426-->
1427
1428</div>
1429
1430<!-- ======================================================================= -->
1431<div class="doc_subsection">
1432 <a name="simplechanges">Making simple changes</a>
1433</div>
1434
1435<div class="doc_text">
1436
1437<p>There are some primitive transformation operations present in the LLVM
Joel Stanley753eb712002-09-11 22:32:24 +0000[diff] [blame]1438infrastructure that are worth knowing about. When performing
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1439transformations, it's fairly common to manipulate the contents of basic
1440blocks. This section describes some of the common methods for doing so
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1441and gives example code.</p>
1442
1443</div>
1444
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1445<!--_______________________________________________________________________-->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1446<div class="doc_subsubsection">
1447 <a name="schanges_creating">Creating and inserting new
1448 <tt>Instruction</tt>s</a>
1449</div>
1450
1451<div class="doc_text">
1452
1453<p><i>Instantiating Instructions</i></p>
1454
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]1455<p>Creation of <tt>Instruction</tt>s is straight-forward: simply call the
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1456constructor for the kind of instruction to instantiate and provide the necessary
1457parameters. For example, an <tt>AllocaInst</tt> only <i>requires</i> a
1458(const-ptr-to) <tt>Type</tt>. Thus:</p>
1459
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1460<div class="doc_code">
1461<pre>
1462AllocaInst* ai = new AllocaInst(Type::IntTy);
1463</pre>
1464</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1465
1466<p>will create an <tt>AllocaInst</tt> instance that represents the allocation of
1467one integer in the current stack frame, at runtime. Each <tt>Instruction</tt>
1468subclass is likely to have varying default parameters which change the semantics
1469of the instruction, so refer to the <a
Misha Brukman31ca1de2004-06-03 23:35:54 +0000[diff] [blame]1470href="/doxygen/classllvm_1_1Instruction.html">doxygen documentation for the subclass of
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1471Instruction</a> that you're interested in instantiating.</p>
1472
1473<p><i>Naming values</i></p>
1474
1475<p>It is very useful to name the values of instructions when you're able to, as
1476this facilitates the debugging of your transformations. If you end up looking
1477at generated LLVM machine code, you definitely want to have logical names
1478associated with the results of instructions! By supplying a value for the
1479<tt>Name</tt> (default) parameter of the <tt>Instruction</tt> constructor, you
1480associate a logical name with the result of the instruction's execution at
1481runtime. For example, say that I'm writing a transformation that dynamically
1482allocates space for an integer on the stack, and that integer is going to be
1483used as some kind of index by some other code. To accomplish this, I place an
1484<tt>AllocaInst</tt> at the first point in the first <tt>BasicBlock</tt> of some
1485<tt>Function</tt>, and I'm intending to use it within the same
1486<tt>Function</tt>. I might do:</p>
1487
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1488<div class="doc_code">
1489<pre>
1490AllocaInst* pa = new AllocaInst(Type::IntTy, 0, "indexLoc");
1491</pre>
1492</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1493
1494<p>where <tt>indexLoc</tt> is now the logical name of the instruction's
1495execution value, which is a pointer to an integer on the runtime stack.</p>
1496
1497<p><i>Inserting instructions</i></p>
1498
1499<p>There are essentially two ways to insert an <tt>Instruction</tt>
1500into an existing sequence of instructions that form a <tt>BasicBlock</tt>:</p>
1501
Joel Stanley9dd1ad62002-09-18 03:17:23 +0000[diff] [blame]1502<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1503 <li>Insertion into an explicit instruction list
1504
1505 <p>Given a <tt>BasicBlock* pb</tt>, an <tt>Instruction* pi</tt> within that
1506 <tt>BasicBlock</tt>, and a newly-created instruction we wish to insert
1507 before <tt>*pi</tt>, we do the following: </p>
1508
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1509<div class="doc_code">
1510<pre>
1511BasicBlock *pb = ...;
1512Instruction *pi = ...;
1513Instruction *newInst = new Instruction(...);
1514
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1515pb-&gt;getInstList().insert(pi, newInst); // <i>Inserts newInst before pi in pb</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1516</pre>
1517</div>
Alkis Evlogimenos9a5dc4f2004-05-27 00:57:51 +0000[diff] [blame]1518
1519 <p>Appending to the end of a <tt>BasicBlock</tt> is so common that
1520 the <tt>Instruction</tt> class and <tt>Instruction</tt>-derived
1521 classes provide constructors which take a pointer to a
1522 <tt>BasicBlock</tt> to be appended to. For example code that
1523 looked like: </p>
1524
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1525<div class="doc_code">
1526<pre>
1527BasicBlock *pb = ...;
1528Instruction *newInst = new Instruction(...);
1529
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1530pb-&gt;getInstList().push_back(newInst); // <i>Appends newInst to pb</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1531</pre>
1532</div>
Alkis Evlogimenos9a5dc4f2004-05-27 00:57:51 +0000[diff] [blame]1533
1534 <p>becomes: </p>
1535
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1536<div class="doc_code">
1537<pre>
1538BasicBlock *pb = ...;
1539Instruction *newInst = new Instruction(..., pb);
1540</pre>
1541</div>
Alkis Evlogimenos9a5dc4f2004-05-27 00:57:51 +0000[diff] [blame]1542
1543 <p>which is much cleaner, especially if you are creating
1544 long instruction streams.</p></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1545
1546 <li>Insertion into an implicit instruction list
1547
1548 <p><tt>Instruction</tt> instances that are already in <tt>BasicBlock</tt>s
1549 are implicitly associated with an existing instruction list: the instruction
1550 list of the enclosing basic block. Thus, we could have accomplished the same
1551 thing as the above code without being given a <tt>BasicBlock</tt> by doing:
1552 </p>
1553
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1554<div class="doc_code">
1555<pre>
1556Instruction *pi = ...;
1557Instruction *newInst = new Instruction(...);
1558
1559pi-&gt;getParent()-&gt;getInstList().insert(pi, newInst);
1560</pre>
1561</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1562
1563 <p>In fact, this sequence of steps occurs so frequently that the
1564 <tt>Instruction</tt> class and <tt>Instruction</tt>-derived classes provide
1565 constructors which take (as a default parameter) a pointer to an
1566 <tt>Instruction</tt> which the newly-created <tt>Instruction</tt> should
1567 precede. That is, <tt>Instruction</tt> constructors are capable of
1568 inserting the newly-created instance into the <tt>BasicBlock</tt> of a
1569 provided instruction, immediately before that instruction. Using an
1570 <tt>Instruction</tt> constructor with a <tt>insertBefore</tt> (default)
1571 parameter, the above code becomes:</p>
1572
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1573<div class="doc_code">
1574<pre>
1575Instruction* pi = ...;
1576Instruction* newInst = new Instruction(..., pi);
1577</pre>
1578</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1579
1580 <p>which is much cleaner, especially if you're creating a lot of
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1581 instructions and adding them to <tt>BasicBlock</tt>s.</p></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1582</ul>
1583
1584</div>
1585
1586<!--_______________________________________________________________________-->
1587<div class="doc_subsubsection">
1588 <a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a>
1589</div>
1590
1591<div class="doc_text">
1592
1593<p>Deleting an instruction from an existing sequence of instructions that form a
Chris Lattner69bf8a92004-05-23 21:06:58 +0000[diff] [blame]1594<a href="#BasicBlock"><tt>BasicBlock</tt></a> is very straight-forward. First,
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1595you must have a pointer to the instruction that you wish to delete. Second, you
1596need to obtain the pointer to that instruction's basic block. You use the
1597pointer to the basic block to get its list of instructions and then use the
1598erase function to remove your instruction. For example:</p>
1599
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1600<div class="doc_code">
1601<pre>
1602<a href="#Instruction">Instruction</a> *I = .. ;
1603<a href="#BasicBlock">BasicBlock</a> *BB = I-&gt;getParent();
1604
1605BB-&gt;getInstList().erase(I);
1606</pre>
1607</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1608
1609</div>
1610
1611<!--_______________________________________________________________________-->
1612<div class="doc_subsubsection">
1613 <a name="schanges_replacing">Replacing an <tt>Instruction</tt> with another
1614 <tt>Value</tt></a>
1615</div>
1616
1617<div class="doc_text">
1618
1619<p><i>Replacing individual instructions</i></p>
1620
1621<p>Including "<a href="/doxygen/BasicBlockUtils_8h-source.html">llvm/Transforms/Utils/BasicBlockUtils.h</a>"
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1622permits use of two very useful replace functions: <tt>ReplaceInstWithValue</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1623and <tt>ReplaceInstWithInst</tt>.</p>
1624
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1625<h4><a name="schanges_deleting">Deleting <tt>Instruction</tt>s</a></h4>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1626
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1627<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1628 <li><tt>ReplaceInstWithValue</tt>
1629
1630 <p>This function replaces all uses (within a basic block) of a given
1631 instruction with a value, and then removes the original instruction. The
1632 following example illustrates the replacement of the result of a particular
Chris Lattner58360822005-01-17 00:12:04 +0000[diff] [blame]1633 <tt>AllocaInst</tt> that allocates memory for a single integer with a null
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1634 pointer to an integer.</p>
1635
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1636<div class="doc_code">
1637<pre>
1638AllocaInst* instToReplace = ...;
1639BasicBlock::iterator ii(instToReplace);
1640
1641ReplaceInstWithValue(instToReplace-&gt;getParent()-&gt;getInstList(), ii,
1642 Constant::getNullValue(PointerType::get(Type::IntTy)));
1643</pre></div></li>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1644
1645 <li><tt>ReplaceInstWithInst</tt>
1646
1647 <p>This function replaces a particular instruction with another
1648 instruction. The following example illustrates the replacement of one
1649 <tt>AllocaInst</tt> with another.</p>
1650
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1651<div class="doc_code">
1652<pre>
1653AllocaInst* instToReplace = ...;
1654BasicBlock::iterator ii(instToReplace);
1655
1656ReplaceInstWithInst(instToReplace-&gt;getParent()-&gt;getInstList(), ii,
1657 new AllocaInst(Type::IntTy, 0, "ptrToReplacedInt"));
1658</pre></div></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]1659</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1660
1661<p><i>Replacing multiple uses of <tt>User</tt>s and <tt>Value</tt>s</i></p>
1662
1663<p>You can use <tt>Value::replaceAllUsesWith</tt> and
1664<tt>User::replaceUsesOfWith</tt> to change more than one use at a time. See the
Chris Lattner00815172007-01-04 22:01:45 +0000[diff] [blame]1665doxygen documentation for the <a href="/doxygen/classllvm_1_1Value.html">Value Class</a>
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]1666and <a href="/doxygen/classllvm_1_1User.html">User Class</a>, respectively, for more
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1667information.</p>
1668
1669<!-- Value::replaceAllUsesWith User::replaceUsesOfWith Point out:
1670include/llvm/Transforms/Utils/ especially BasicBlockUtils.h with:
1671ReplaceInstWithValue, ReplaceInstWithInst -->
1672
1673</div>
1674
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]1675<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]1676<div class="doc_section">
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1677 <a name="advanced">Advanced Topics</a>
1678</div>
1679<!-- *********************************************************************** -->
1680
1681<div class="doc_text">
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1682<p>
1683This section describes some of the advanced or obscure API's that most clients
1684do not need to be aware of. These API's tend manage the inner workings of the
1685LLVM system, and only need to be accessed in unusual circumstances.
1686</p>
1687</div>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1688
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1689<!-- ======================================================================= -->
1690<div class="doc_subsection">
1691 <a name="TypeResolve">LLVM Type Resolution</a>
1692</div>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1693
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1694<div class="doc_text">
1695
1696<p>
1697The LLVM type system has a very simple goal: allow clients to compare types for
1698structural equality with a simple pointer comparison (aka a shallow compare).
1699This goal makes clients much simpler and faster, and is used throughout the LLVM
1700system.
1701</p>
1702
1703<p>
1704Unfortunately achieving this goal is not a simple matter. In particular,
1705recursive types and late resolution of opaque types makes the situation very
1706difficult to handle. Fortunately, for the most part, our implementation makes
1707most clients able to be completely unaware of the nasty internal details. The
1708primary case where clients are exposed to the inner workings of it are when
1709building a recursive type. In addition to this case, the LLVM bytecode reader,
1710assembly parser, and linker also have to be aware of the inner workings of this
1711system.
1712</p>
1713
Chris Lattner0f876db2005-04-25 15:47:57 +0000[diff] [blame]1714<p>
1715For our purposes below, we need three concepts. First, an "Opaque Type" is
1716exactly as defined in the <a href="LangRef.html#t_opaque">language
1717reference</a>. Second an "Abstract Type" is any type which includes an
Reid Spencer06565dc2007-01-12 17:11:23 +0000[diff] [blame]1718opaque type as part of its type graph (for example "<tt>{ opaque, i32 }</tt>").
1719Third, a concrete type is a type that is not an abstract type (e.g. "<tt>{ i32,
Chris Lattner0f876db2005-04-25 15:47:57 +0000[diff] [blame]1720float }</tt>").
1721</p>
1722
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1723</div>
1724
1725<!-- ______________________________________________________________________ -->
1726<div class="doc_subsubsection">
1727 <a name="BuildRecType">Basic Recursive Type Construction</a>
1728</div>
1729
1730<div class="doc_text">
1731
1732<p>
1733Because the most common question is "how do I build a recursive type with LLVM",
1734we answer it now and explain it as we go. Here we include enough to cause this
1735to be emitted to an output .ll file:
1736</p>
1737
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1738<div class="doc_code">
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1739<pre>
Reid Spencer06565dc2007-01-12 17:11:23 +0000[diff] [blame]1740%mylist = type { %mylist*, i32 }
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1741</pre>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1742</div>
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1743
1744<p>
1745To build this, use the following LLVM APIs:
1746</p>
1747
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1748<div class="doc_code">
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1749<pre>
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1750// <i>Create the initial outer struct</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1751<a href="#PATypeHolder">PATypeHolder</a> StructTy = OpaqueType::get();
1752std::vector&lt;const Type*&gt; Elts;
1753Elts.push_back(PointerType::get(StructTy));
1754Elts.push_back(Type::IntTy);
1755StructType *NewSTy = StructType::get(Elts);
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1756
Reid Spencer06565dc2007-01-12 17:11:23 +0000[diff] [blame]1757// <i>At this point, NewSTy = "{ opaque*, i32 }". Tell VMCore that</i>
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1758// <i>the struct and the opaque type are actually the same.</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1759cast&lt;OpaqueType&gt;(StructTy.get())-&gt;<a href="#refineAbstractTypeTo">refineAbstractTypeTo</a>(NewSTy);
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1760
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1761// <i>NewSTy is potentially invalidated, but StructTy (a <a href="#PATypeHolder">PATypeHolder</a>) is</i>
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1762// <i>kept up-to-date</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1763NewSTy = cast&lt;StructType&gt;(StructTy.get());
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1764
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1765// <i>Add a name for the type to the module symbol table (optional)</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1766MyModule-&gt;addTypeName("mylist", NewSTy);
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1767</pre>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1768</div>
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1769
1770<p>
1771This code shows the basic approach used to build recursive types: build a
1772non-recursive type using 'opaque', then use type unification to close the cycle.
1773The type unification step is performed by the <tt><a
Chris Lattneraff26d12007-02-03 03:06:52 +0000[diff] [blame]1774href="#refineAbstractTypeTo">refineAbstractTypeTo</a></tt> method, which is
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1775described next. After that, we describe the <a
1776href="#PATypeHolder">PATypeHolder class</a>.
1777</p>
1778
1779</div>
1780
1781<!-- ______________________________________________________________________ -->
1782<div class="doc_subsubsection">
1783 <a name="refineAbstractTypeTo">The <tt>refineAbstractTypeTo</tt> method</a>
1784</div>
1785
1786<div class="doc_text">
1787<p>
1788The <tt>refineAbstractTypeTo</tt> method starts the type unification process.
1789While this method is actually a member of the DerivedType class, it is most
1790often used on OpaqueType instances. Type unification is actually a recursive
1791process. After unification, types can become structurally isomorphic to
1792existing types, and all duplicates are deleted (to preserve pointer equality).
1793</p>
1794
1795<p>
1796In the example above, the OpaqueType object is definitely deleted.
Reid Spencer06565dc2007-01-12 17:11:23 +0000[diff] [blame]1797Additionally, if there is an "{ \2*, i32}" type already created in the system,
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1798the pointer and struct type created are <b>also</b> deleted. Obviously whenever
1799a type is deleted, any "Type*" pointers in the program are invalidated. As
1800such, it is safest to avoid having <i>any</i> "Type*" pointers to abstract types
1801live across a call to <tt>refineAbstractTypeTo</tt> (note that non-abstract
1802types can never move or be deleted). To deal with this, the <a
1803href="#PATypeHolder">PATypeHolder</a> class is used to maintain a stable
1804reference to a possibly refined type, and the <a
1805href="#AbstractTypeUser">AbstractTypeUser</a> class is used to update more
1806complex datastructures.
1807</p>
1808
1809</div>
1810
1811<!-- ______________________________________________________________________ -->
1812<div class="doc_subsubsection">
1813 <a name="PATypeHolder">The PATypeHolder Class</a>
1814</div>
1815
1816<div class="doc_text">
1817<p>
1818PATypeHolder is a form of a "smart pointer" for Type objects. When VMCore
1819happily goes about nuking types that become isomorphic to existing types, it
1820automatically updates all PATypeHolder objects to point to the new type. In the
1821example above, this allows the code to maintain a pointer to the resultant
1822resolved recursive type, even though the Type*'s are potentially invalidated.
1823</p>
1824
1825<p>
1826PATypeHolder is an extremely light-weight object that uses a lazy union-find
1827implementation to update pointers. For example the pointer from a Value to its
1828Type is maintained by PATypeHolder objects.
1829</p>
1830
1831</div>
1832
1833<!-- ______________________________________________________________________ -->
1834<div class="doc_subsubsection">
1835 <a name="AbstractTypeUser">The AbstractTypeUser Class</a>
1836</div>
1837
1838<div class="doc_text">
1839
1840<p>
1841Some data structures need more to perform more complex updates when types get
1842resolved. The <a href="#SymbolTable">SymbolTable</a> class, for example, needs
1843move and potentially merge type planes in its representation when a pointer
1844changes.</p>
1845
1846<p>
1847To support this, a class can derive from the AbstractTypeUser class. This class
1848allows it to get callbacks when certain types are resolved. To register to get
1849callbacks for a particular type, the DerivedType::{add/remove}AbstractTypeUser
Chris Lattner0f876db2005-04-25 15:47:57 +0000[diff] [blame]1850methods can be called on a type. Note that these methods only work for <i>
Reid Spencer06565dc2007-01-12 17:11:23 +0000[diff] [blame]1851 abstract</i> types. Concrete types (those that do not include any opaque
1852objects) can never be refined.
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1853</p>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1854</div>
1855
1856
1857<!-- ======================================================================= -->
1858<div class="doc_subsection">
1859 <a name="SymbolTable">The <tt>SymbolTable</tt> class</a>
1860</div>
Chris Lattnerf1b200b2005-04-23 17:27:36 +0000[diff] [blame]1861
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1862<div class="doc_text">
1863<p>This class provides a symbol table that the <a
1864href="#Function"><tt>Function</tt></a> and <a href="#Module">
1865<tt>Module</tt></a> classes use for naming definitions. The symbol table can
Reid Spencera6362242007-01-07 00:41:39 +0000[diff] [blame]1866provide a name for any <a href="#Value"><tt>Value</tt></a>.
1867<tt>SymbolTable</tt> is an abstract data type. It hides the data it contains
1868and provides access to it through a controlled interface.</p>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1869
Reid Spencera6362242007-01-07 00:41:39 +0000[diff] [blame]1870<p>Note that the <tt>SymbolTable</tt> class should not be directly accessed
1871by most clients. It should only be used when iteration over the symbol table
1872names themselves are required, which is very special purpose. Note that not
1873all LLVM
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1874<a href="#Value">Value</a>s have names, and those without names (i.e. they have
1875an empty name) do not exist in the symbol table.
1876</p>
1877
1878<p>To use the <tt>SymbolTable</tt> well, you need to understand the
1879structure of the information it holds. The class contains two
1880<tt>std::map</tt> objects. The first, <tt>pmap</tt>, is a map of
1881<tt>Type*</tt> to maps of name (<tt>std::string</tt>) to <tt>Value*</tt>.
Reid Spencera6362242007-01-07 00:41:39 +0000[diff] [blame]1882Thus, Values are stored in two-dimensions and accessed by <tt>Type</tt> and
1883name.</p>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1884
1885<p>The interface of this class provides three basic types of operations:
1886<ol>
1887 <li><em>Accessors</em>. Accessors provide read-only access to information
1888 such as finding a value for a name with the
1889 <a href="#SymbolTable_lookup">lookup</a> method.</li>
1890 <li><em>Mutators</em>. Mutators allow the user to add information to the
1891 <tt>SymbolTable</tt> with methods like
1892 <a href="#SymbolTable_insert"><tt>insert</tt></a>.</li>
1893 <li><em>Iterators</em>. Iterators allow the user to traverse the content
1894 of the symbol table in well defined ways, such as the method
Reid Spencera6362242007-01-07 00:41:39 +0000[diff] [blame]1895 <a href="#SymbolTable_plane_begin"><tt>plane_begin</tt></a>.</li>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1896</ol>
1897
1898<h3>Accessors</h3>
1899<dl>
1900 <dt><tt>Value* lookup(const Type* Ty, const std::string&amp; name) const</tt>:
1901 </dt>
1902 <dd>The <tt>lookup</tt> method searches the type plane given by the
1903 <tt>Ty</tt> parameter for a <tt>Value</tt> with the provided <tt>name</tt>.
1904 If a suitable <tt>Value</tt> is not found, null is returned.</dd>
1905
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1906 <dt><tt>bool isEmpty() const</tt>:</dt>
1907 <dd>This function returns true if both the value and types maps are
1908 empty</dd>
1909</dl>
1910
1911<h3>Mutators</h3>
1912<dl>
1913 <dt><tt>void insert(Value *Val)</tt>:</dt>
1914 <dd>This method adds the provided value to the symbol table. The Value must
1915 have both a name and a type which are extracted and used to place the value
1916 in the correct type plane under the value's name.</dd>
1917
1918 <dt><tt>void insert(const std::string&amp; Name, Value *Val)</tt>:</dt>
1919 <dd> Inserts a constant or type into the symbol table with the specified
1920 name. There can be a many to one mapping between names and constants
1921 or types.</dd>
1922
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1923 <dt><tt>void remove(Value* Val)</tt>:</dt>
1924 <dd> This method removes a named value from the symbol table. The
1925 type and name of the Value are extracted from \p N and used to
1926 lookup the Value in the correct type plane. If the Value is
1927 not in the symbol table, this method silently ignores the
1928 request.</dd>
1929
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1930 <dt><tt>Value* remove(const std::string&amp; Name, Value *Val)</tt>:</dt>
1931 <dd> Remove a constant or type with the specified name from the
1932 symbol table.</dd>
1933
Reid Spencera6362242007-01-07 00:41:39 +0000[diff] [blame]1934 <dt><tt>Value *remove(const value_iterator&amp; It)</tt>:</dt>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1935 <dd> Removes a specific value from the symbol table.
1936 Returns the removed value.</dd>
1937
1938 <dt><tt>bool strip()</tt>:</dt>
1939 <dd> This method will strip the symbol table of its names leaving
1940 the type and values. </dd>
1941
1942 <dt><tt>void clear()</tt>:</dt>
1943 <dd>Empty the symbol table completely.</dd>
1944</dl>
1945
1946<h3>Iteration</h3>
1947<p>The following functions describe three types of iterators you can obtain
1948the beginning or end of the sequence for both const and non-const. It is
1949important to keep track of the different kinds of iterators. There are
1950three idioms worth pointing out:</p>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1951
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1952<table>
1953 <tr><th>Units</th><th>Iterator</th><th>Idiom</th></tr>
1954 <tr>
1955 <td align="left">Planes Of name/Value maps</td><td>PI</td>
1956 <td align="left"><pre><tt>
1957for (SymbolTable::plane_const_iterator PI = ST.plane_begin(),
1958 PE = ST.plane_end(); PI != PE; ++PI ) {
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1959 PI-&gt;first // <i>This is the Type* of the plane</i>
1960 PI-&gt;second // <i>This is the SymbolTable::ValueMap of name/Value pairs</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1961}
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1962 </tt></pre></td>
1963 </tr>
1964 <tr>
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1965 <td align="left">name/Value pairs in a plane</td><td>VI</td>
1966 <td align="left"><pre><tt>
1967for (SymbolTable::value_const_iterator VI = ST.value_begin(SomeType),
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1968 VE = ST.value_end(SomeType); VI != VE; ++VI ) {
Bill Wendling82e2eea2006-10-11 18:00:22 +0000[diff] [blame]1969 VI-&gt;first // <i>This is the name of the Value</i>
1970 VI-&gt;second // <i>This is the Value* value associated with the name</i>
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]1971}
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]1972 </tt></pre></td>
1973 </tr>
1974</table>
1975
1976<p>Using the recommended iterator names and idioms will help you avoid
1977making mistakes. Of particular note, make sure that whenever you use
1978value_begin(SomeType) that you always compare the resulting iterator
1979with value_end(SomeType) not value_end(SomeOtherType) or else you
1980will loop infinitely.</p>
1981
1982<dl>
1983
1984 <dt><tt>plane_iterator plane_begin()</tt>:</dt>
1985 <dd>Get an iterator that starts at the beginning of the type planes.
1986 The iterator will iterate over the Type/ValueMap pairs in the
1987 type planes. </dd>
1988
1989 <dt><tt>plane_const_iterator plane_begin() const</tt>:</dt>
1990 <dd>Get a const_iterator that starts at the beginning of the type
1991 planes. The iterator will iterate over the Type/ValueMap pairs
1992 in the type planes. </dd>
1993
1994 <dt><tt>plane_iterator plane_end()</tt>:</dt>
1995 <dd>Get an iterator at the end of the type planes. This serves as
1996 the marker for end of iteration over the type planes.</dd>
1997
1998 <dt><tt>plane_const_iterator plane_end() const</tt>:</dt>
1999 <dd>Get a const_iterator at the end of the type planes. This serves as
2000 the marker for end of iteration over the type planes.</dd>
2001
2002 <dt><tt>value_iterator value_begin(const Type *Typ)</tt>:</dt>
2003 <dd>Get an iterator that starts at the beginning of a type plane.
2004 The iterator will iterate over the name/value pairs in the type plane.
2005 Note: The type plane must already exist before using this.</dd>
2006
2007 <dt><tt>value_const_iterator value_begin(const Type *Typ) const</tt>:</dt>
2008 <dd>Get a const_iterator that starts at the beginning of a type plane.
2009 The iterator will iterate over the name/value pairs in the type plane.
2010 Note: The type plane must already exist before using this.</dd>
2011
2012 <dt><tt>value_iterator value_end(const Type *Typ)</tt>:</dt>
2013 <dd>Get an iterator to the end of a type plane. This serves as the marker
2014 for end of iteration of the type plane.
2015 Note: The type plane must already exist before using this.</dd>
2016
2017 <dt><tt>value_const_iterator value_end(const Type *Typ) const</tt>:</dt>
2018 <dd>Get a const_iterator to the end of a type plane. This serves as the
2019 marker for end of iteration of the type plane.
2020 Note: the type plane must already exist before using this.</dd>
2021
Chris Lattnerd9d6e102005-04-23 16:10:52 +0000[diff] [blame]2022 <dt><tt>plane_const_iterator find(const Type* Typ ) const</tt>:</dt>
2023 <dd>This method returns a plane_const_iterator for iteration over
2024 the type planes starting at a specific plane, given by \p Ty.</dd>
2025
2026 <dt><tt>plane_iterator find( const Type* Typ </tt>:</dt>
2027 <dd>This method returns a plane_iterator for iteration over the
2028 type planes starting at a specific plane, given by \p Ty.</dd>
2029
2030</dl>
2031</div>
2032
2033
2034
2035<!-- *********************************************************************** -->
2036<div class="doc_section">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2037 <a name="coreclasses">The Core LLVM Class Hierarchy Reference </a>
2038</div>
2039<!-- *********************************************************************** -->
2040
2041<div class="doc_text">
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]2042<p><tt>#include "<a href="/doxygen/Type_8h-source.html">llvm/Type.h</a>"</tt>
2043<br>doxygen info: <a href="/doxygen/classllvm_1_1Type.html">Type Class</a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2044
2045<p>The Core LLVM classes are the primary means of representing the program
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2046being inspected or transformed. The core LLVM classes are defined in
2047header files in the <tt>include/llvm/</tt> directory, and implemented in
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2048the <tt>lib/VMCore</tt> directory.</p>
2049
2050</div>
2051
2052<!-- ======================================================================= -->
2053<div class="doc_subsection">
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]2054 <a name="Type">The <tt>Type</tt> class and Derived Types</a>
2055</div>
2056
2057<div class="doc_text">
2058
2059 <p><tt>Type</tt> is a superclass of all type classes. Every <tt>Value</tt> has
2060 a <tt>Type</tt>. <tt>Type</tt> cannot be instantiated directly but only
2061 through its subclasses. Certain primitive types (<tt>VoidType</tt>,
2062 <tt>LabelType</tt>, <tt>FloatType</tt> and <tt>DoubleType</tt>) have hidden
2063 subclasses. They are hidden because they offer no useful functionality beyond
2064 what the <tt>Type</tt> class offers except to distinguish themselves from
2065 other subclasses of <tt>Type</tt>.</p>
2066 <p>All other types are subclasses of <tt>DerivedType</tt>. Types can be
2067 named, but this is not a requirement. There exists exactly
2068 one instance of a given shape at any one time. This allows type equality to
2069 be performed with address equality of the Type Instance. That is, given two
2070 <tt>Type*</tt> values, the types are identical if the pointers are identical.
2071 </p>
2072</div>
2073
2074<!-- _______________________________________________________________________ -->
2075<div class="doc_subsubsection">
2076 <a name="m_Value">Important Public Methods</a>
2077</div>
2078
2079<div class="doc_text">
2080
2081<ul>
Chris Lattner8f79df32007-01-15 01:55:32 +0000[diff] [blame]2082 <li><tt>bool isInteger() const</tt>: Returns true for any integer type.</li>
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]2083
2084 <li><tt>bool isFloatingPoint()</tt>: Return true if this is one of the two
2085 floating point types.</li>
2086
2087 <li><tt>bool isAbstract()</tt>: Return true if the type is abstract (contains
2088 an OpaqueType anywhere in its definition).</li>
2089
2090 <li><tt>bool isSized()</tt>: Return true if the type has known size. Things
2091 that don't have a size are abstract types, labels and void.</li>
2092
2093</ul>
2094</div>
2095
2096<!-- _______________________________________________________________________ -->
2097<div class="doc_subsubsection">
2098 <a name="m_Value">Important Derived Types</a>
2099</div>
2100<div class="doc_text">
2101<dl>
2102 <dt><tt>IntegerType</tt></dt>
2103 <dd>Subclass of DerivedType that represents integer types of any bit width.
2104 Any bit width between <tt>IntegerType::MIN_INT_BITS</tt> (1) and
2105 <tt>IntegerType::MAX_INT_BITS</tt> (~8 million) can be represented.
2106 <ul>
2107 <li><tt>static const IntegerType* get(unsigned NumBits)</tt>: get an integer
2108 type of a specific bit width.</li>
2109 <li><tt>unsigned getBitWidth() const</tt>: Get the bit width of an integer
2110 type.</li>
2111 </ul>
2112 </dd>
2113 <dt><tt>SequentialType</tt></dt>
2114 <dd>This is subclassed by ArrayType and PointerType
2115 <ul>
2116 <li><tt>const Type * getElementType() const</tt>: Returns the type of each
2117 of the elements in the sequential type. </li>
2118 </ul>
2119 </dd>
2120 <dt><tt>ArrayType</tt></dt>
2121 <dd>This is a subclass of SequentialType and defines the interface for array
2122 types.
2123 <ul>
2124 <li><tt>unsigned getNumElements() const</tt>: Returns the number of
2125 elements in the array. </li>
2126 </ul>
2127 </dd>
2128 <dt><tt>PointerType</tt></dt>
Chris Lattner302da1e2007-02-03 03:05:57 +0000[diff] [blame]2129 <dd>Subclass of SequentialType for pointer types.</dd>
Reid Spencer303c4b42007-01-12 17:26:25 +0000[diff] [blame]2130 <dt><tt>PackedType</tt></dt>
2131 <dd>Subclass of SequentialType for packed (vector) types. A
2132 packed type is similar to an ArrayType but is distinguished because it is
2133 a first class type wherease ArrayType is not. Packed types are used for
2134 vector operations and are usually small vectors of of an integer or floating
2135 point type.</dd>
2136 <dt><tt>StructType</tt></dt>
2137 <dd>Subclass of DerivedTypes for struct types.</dd>
2138 <dt><tt>FunctionType</tt></dt>
2139 <dd>Subclass of DerivedTypes for function types.
2140 <ul>
2141 <li><tt>bool isVarArg() const</tt>: Returns true if its a vararg
2142 function</li>
2143 <li><tt> const Type * getReturnType() const</tt>: Returns the
2144 return type of the function.</li>
2145 <li><tt>const Type * getParamType (unsigned i)</tt>: Returns
2146 the type of the ith parameter.</li>
2147 <li><tt> const unsigned getNumParams() const</tt>: Returns the
2148 number of formal parameters.</li>
2149 </ul>
2150 </dd>
2151 <dt><tt>OpaqueType</tt></dt>
2152 <dd>Sublcass of DerivedType for abstract types. This class
2153 defines no content and is used as a placeholder for some other type. Note
2154 that OpaqueType is used (temporarily) during type resolution for forward
2155 references of types. Once the referenced type is resolved, the OpaqueType
2156 is replaced with the actual type. OpaqueType can also be used for data
2157 abstraction. At link time opaque types can be resolved to actual types
2158 of the same name.</dd>
2159</dl>
2160</div>
2161
2162<!-- ======================================================================= -->
2163<div class="doc_subsection">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2164 <a name="Value">The <tt>Value</tt> class</a>
2165</div>
2166
2167<div>
2168
2169<p><tt>#include "<a href="/doxygen/Value_8h-source.html">llvm/Value.h</a>"</tt>
2170<br>
Chris Lattner00815172007-01-04 22:01:45 +0000[diff] [blame]2171doxygen info: <a href="/doxygen/classllvm_1_1Value.html">Value Class</a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2172
2173<p>The <tt>Value</tt> class is the most important class in the LLVM Source
2174base. It represents a typed value that may be used (among other things) as an
2175operand to an instruction. There are many different types of <tt>Value</tt>s,
2176such as <a href="#Constant"><tt>Constant</tt></a>s,<a
2177href="#Argument"><tt>Argument</tt></a>s. Even <a
2178href="#Instruction"><tt>Instruction</tt></a>s and <a
2179href="#Function"><tt>Function</tt></a>s are <tt>Value</tt>s.</p>
2180
2181<p>A particular <tt>Value</tt> may be used many times in the LLVM representation
2182for a program. For example, an incoming argument to a function (represented
2183with an instance of the <a href="#Argument">Argument</a> class) is "used" by
2184every instruction in the function that references the argument. To keep track
2185of this relationship, the <tt>Value</tt> class keeps a list of all of the <a
2186href="#User"><tt>User</tt></a>s that is using it (the <a
2187href="#User"><tt>User</tt></a> class is a base class for all nodes in the LLVM
2188graph that can refer to <tt>Value</tt>s). This use list is how LLVM represents
2189def-use information in the program, and is accessible through the <tt>use_</tt>*
2190methods, shown below.</p>
2191
2192<p>Because LLVM is a typed representation, every LLVM <tt>Value</tt> is typed,
2193and this <a href="#Type">Type</a> is available through the <tt>getType()</tt>
2194method. In addition, all LLVM values can be named. The "name" of the
2195<tt>Value</tt> is a symbolic string printed in the LLVM code:</p>
2196
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2197<div class="doc_code">
2198<pre>
Reid Spencer06565dc2007-01-12 17:11:23 +0000[diff] [blame]2199%<b>foo</b> = add i32 1, 2
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2200</pre>
2201</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2202
2203<p><a name="#nameWarning">The name of this instruction is "foo".</a> <b>NOTE</b>
2204that the name of any value may be missing (an empty string), so names should
2205<b>ONLY</b> be used for debugging (making the source code easier to read,
2206debugging printouts), they should not be used to keep track of values or map
2207between them. For this purpose, use a <tt>std::map</tt> of pointers to the
2208<tt>Value</tt> itself instead.</p>
2209
2210<p>One important aspect of LLVM is that there is no distinction between an SSA
2211variable and the operation that produces it. Because of this, any reference to
2212the value produced by an instruction (or the value available as an incoming
Chris Lattnerd5fc4fc2004-03-18 14:58:55 +0000[diff] [blame]2213argument, for example) is represented as a direct pointer to the instance of
2214the class that
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2215represents this value. Although this may take some getting used to, it
2216simplifies the representation and makes it easier to manipulate.</p>
2217
2218</div>
2219
2220<!-- _______________________________________________________________________ -->
2221<div class="doc_subsubsection">
2222 <a name="m_Value">Important Public Members of the <tt>Value</tt> class</a>
2223</div>
2224
2225<div class="doc_text">
2226
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2227<ul>
2228 <li><tt>Value::use_iterator</tt> - Typedef for iterator over the
2229use-list<br>
2230 <tt>Value::use_const_iterator</tt> - Typedef for const_iterator over
2231the use-list<br>
2232 <tt>unsigned use_size()</tt> - Returns the number of users of the
2233value.<br>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]2234 <tt>bool use_empty()</tt> - Returns true if there are no users.<br>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2235 <tt>use_iterator use_begin()</tt> - Get an iterator to the start of
2236the use-list.<br>
2237 <tt>use_iterator use_end()</tt> - Get an iterator to the end of the
2238use-list.<br>
2239 <tt><a href="#User">User</a> *use_back()</tt> - Returns the last
2240element in the list.
2241 <p> These methods are the interface to access the def-use
2242information in LLVM. As with all other iterators in LLVM, the naming
2243conventions follow the conventions defined by the <a href="#stl">STL</a>.</p>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2244 </li>
2245 <li><tt><a href="#Type">Type</a> *getType() const</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2246 <p>This method returns the Type of the Value.</p>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2247 </li>
2248 <li><tt>bool hasName() const</tt><br>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]2249 <tt>std::string getName() const</tt><br>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2250 <tt>void setName(const std::string &amp;Name)</tt>
2251 <p> This family of methods is used to access and assign a name to a <tt>Value</tt>,
2252be aware of the <a href="#nameWarning">precaution above</a>.</p>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2253 </li>
2254 <li><tt>void replaceAllUsesWith(Value *V)</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2255
2256 <p>This method traverses the use list of a <tt>Value</tt> changing all <a
2257 href="#User"><tt>User</tt>s</a> of the current value to refer to
2258 "<tt>V</tt>" instead. For example, if you detect that an instruction always
2259 produces a constant value (for example through constant folding), you can
2260 replace all uses of the instruction with the constant like this:</p>
2261
Bill Wendling3cd5ca62006-10-11 06:30:10 +0000[diff] [blame]2262<div class="doc_code">
2263<pre>
2264Inst-&gt;replaceAllUsesWith(ConstVal);
2265</pre>
2266</div>
2267
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2268</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2269
2270</div>
2271
2272<!-- ======================================================================= -->
2273<div class="doc_subsection">
2274 <a name="User">The <tt>User</tt> class</a>
2275</div>
2276
2277<div class="doc_text">
2278
2279<p>
2280<tt>#include "<a href="/doxygen/User_8h-source.html">llvm/User.h</a>"</tt><br>
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]2281doxygen info: <a href="/doxygen/classllvm_1_1User.html">User Class</a><br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2282Superclass: <a href="#Value"><tt>Value</tt></a></p>
2283
2284<p>The <tt>User</tt> class is the common base class of all LLVM nodes that may
2285refer to <a href="#Value"><tt>Value</tt></a>s. It exposes a list of "Operands"
2286that are all of the <a href="#Value"><tt>Value</tt></a>s that the User is
2287referring to. The <tt>User</tt> class itself is a subclass of
2288<tt>Value</tt>.</p>
2289
2290<p>The operands of a <tt>User</tt> point directly to the LLVM <a
2291href="#Value"><tt>Value</tt></a> that it refers to. Because LLVM uses Static
2292Single Assignment (SSA) form, there can only be one definition referred to,
2293allowing this direct connection. This connection provides the use-def
2294information in LLVM.</p>
2295
2296</div>
2297
2298<!-- _______________________________________________________________________ -->
2299<div class="doc_subsubsection">
2300 <a name="m_User">Important Public Members of the <tt>User</tt> class</a>
2301</div>
2302
2303<div class="doc_text">
2304
2305<p>The <tt>User</tt> class exposes the operand list in two ways: through
2306an index access interface and through an iterator based interface.</p>
2307
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2308<ul>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2309 <li><tt>Value *getOperand(unsigned i)</tt><br>
2310 <tt>unsigned getNumOperands()</tt>
2311 <p> These two methods expose the operands of the <tt>User</tt> in a
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2312convenient form for direct access.</p></li>
2313
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2314 <li><tt>User::op_iterator</tt> - Typedef for iterator over the operand
2315list<br>
Chris Lattner58360822005-01-17 00:12:04 +0000[diff] [blame]2316 <tt>op_iterator op_begin()</tt> - Get an iterator to the start of
2317the operand list.<br>
2318 <tt>op_iterator op_end()</tt> - Get an iterator to the end of the
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2319operand list.
2320 <p> Together, these methods make up the iterator based interface to
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2321the operands of a <tt>User</tt>.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2322</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2323
2324</div>
2325
2326<!-- ======================================================================= -->
2327<div class="doc_subsection">
2328 <a name="Instruction">The <tt>Instruction</tt> class</a>
2329</div>
2330
2331<div class="doc_text">
2332
2333<p><tt>#include "</tt><tt><a
2334href="/doxygen/Instruction_8h-source.html">llvm/Instruction.h</a>"</tt><br>
Misha Brukman31ca1de2004-06-03 23:35:54 +0000[diff] [blame]2335doxygen info: <a href="/doxygen/classllvm_1_1Instruction.html">Instruction Class</a><br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2336Superclasses: <a href="#User"><tt>User</tt></a>, <a
2337href="#Value"><tt>Value</tt></a></p>
2338
2339<p>The <tt>Instruction</tt> class is the common base class for all LLVM
2340instructions. It provides only a few methods, but is a very commonly used
2341class. The primary data tracked by the <tt>Instruction</tt> class itself is the
2342opcode (instruction type) and the parent <a
2343href="#BasicBlock"><tt>BasicBlock</tt></a> the <tt>Instruction</tt> is embedded
2344into. To represent a specific type of instruction, one of many subclasses of
2345<tt>Instruction</tt> are used.</p>
2346
2347<p> Because the <tt>Instruction</tt> class subclasses the <a
2348href="#User"><tt>User</tt></a> class, its operands can be accessed in the same
2349way as for other <a href="#User"><tt>User</tt></a>s (with the
2350<tt>getOperand()</tt>/<tt>getNumOperands()</tt> and
2351<tt>op_begin()</tt>/<tt>op_end()</tt> methods).</p> <p> An important file for
2352the <tt>Instruction</tt> class is the <tt>llvm/Instruction.def</tt> file. This
2353file contains some meta-data about the various different types of instructions
2354in LLVM. It describes the enum values that are used as opcodes (for example
Reid Spencerc92d25d2006-12-19 19:47:19 +0000[diff] [blame]2355<tt>Instruction::Add</tt> and <tt>Instruction::ICmp</tt>), as well as the
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2356concrete sub-classes of <tt>Instruction</tt> that implement the instruction (for
2357example <tt><a href="#BinaryOperator">BinaryOperator</a></tt> and <tt><a
Reid Spencerc92d25d2006-12-19 19:47:19 +0000[diff] [blame]2358href="#CmpInst">CmpInst</a></tt>). Unfortunately, the use of macros in
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2359this file confuses doxygen, so these enum values don't show up correctly in the
Misha Brukman31ca1de2004-06-03 23:35:54 +0000[diff] [blame]2360<a href="/doxygen/classllvm_1_1Instruction.html">doxygen output</a>.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2361
2362</div>
2363
2364<!-- _______________________________________________________________________ -->
2365<div class="doc_subsubsection">
Reid Spencerc92d25d2006-12-19 19:47:19 +0000[diff] [blame]2366 <a name="s_Instruction">Important Subclasses of the <tt>Instruction</tt>
2367 class</a>
2368</div>
2369<div class="doc_text">
2370 <ul>
2371 <li><tt><a name="BinaryOperator">BinaryOperator</a></tt>
2372 <p>This subclasses represents all two operand instructions whose operands
2373 must be the same type, except for the comparison instructions.</p></li>
2374 <li><tt><a name="CastInst">CastInst</a></tt>
2375 <p>This subclass is the parent of the 12 casting instructions. It provides
2376 common operations on cast instructions.</p>
2377 <li><tt><a name="CmpInst">CmpInst</a></tt>
2378 <p>This subclass respresents the two comparison instructions,
2379 <a href="LangRef.html#i_icmp">ICmpInst</a> (integer opreands), and
2380 <a href="LangRef.html#i_fcmp">FCmpInst</a> (floating point operands).</p>
2381 <li><tt><a name="TerminatorInst">TerminatorInst</a></tt>
2382 <p>This subclass is the parent of all terminator instructions (those which
2383 can terminate a block).</p>
2384 </ul>
2385 </div>
2386
2387<!-- _______________________________________________________________________ -->
2388<div class="doc_subsubsection">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2389 <a name="m_Instruction">Important Public Members of the <tt>Instruction</tt>
2390 class</a>
2391</div>
2392
2393<div class="doc_text">
2394
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2395<ul>
2396 <li><tt><a href="#BasicBlock">BasicBlock</a> *getParent()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2397 <p>Returns the <a href="#BasicBlock"><tt>BasicBlock</tt></a> that
2398this <tt>Instruction</tt> is embedded into.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2399 <li><tt>bool mayWriteToMemory()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2400 <p>Returns true if the instruction writes to memory, i.e. it is a
2401 <tt>call</tt>,<tt>free</tt>,<tt>invoke</tt>, or <tt>store</tt>.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2402 <li><tt>unsigned getOpcode()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2403 <p>Returns the opcode for the <tt>Instruction</tt>.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2404 <li><tt><a href="#Instruction">Instruction</a> *clone() const</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2405 <p>Returns another instance of the specified instruction, identical
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2406in all ways to the original except that the instruction has no parent
2407(ie it's not embedded into a <a href="#BasicBlock"><tt>BasicBlock</tt></a>),
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2408and it has no name</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2409</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2410
2411</div>
2412
2413<!-- ======================================================================= -->
2414<div class="doc_subsection">
2415 <a name="BasicBlock">The <tt>BasicBlock</tt> class</a>
2416</div>
2417
2418<div class="doc_text">
2419
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]2420<p><tt>#include "<a
2421href="/doxygen/BasicBlock_8h-source.html">llvm/BasicBlock.h</a>"</tt><br>
2422doxygen info: <a href="/doxygen/structllvm_1_1BasicBlock.html">BasicBlock
2423Class</a><br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2424Superclass: <a href="#Value"><tt>Value</tt></a></p>
2425
2426<p>This class represents a single entry multiple exit section of the code,
2427commonly known as a basic block by the compiler community. The
2428<tt>BasicBlock</tt> class maintains a list of <a
2429href="#Instruction"><tt>Instruction</tt></a>s, which form the body of the block.
2430Matching the language definition, the last element of this list of instructions
2431is always a terminator instruction (a subclass of the <a
2432href="#TerminatorInst"><tt>TerminatorInst</tt></a> class).</p>
2433
2434<p>In addition to tracking the list of instructions that make up the block, the
2435<tt>BasicBlock</tt> class also keeps track of the <a
2436href="#Function"><tt>Function</tt></a> that it is embedded into.</p>
2437
2438<p>Note that <tt>BasicBlock</tt>s themselves are <a
2439href="#Value"><tt>Value</tt></a>s, because they are referenced by instructions
2440like branches and can go in the switch tables. <tt>BasicBlock</tt>s have type
2441<tt>label</tt>.</p>
2442
2443</div>
2444
2445<!-- _______________________________________________________________________ -->
2446<div class="doc_subsubsection">
2447 <a name="m_BasicBlock">Important Public Members of the <tt>BasicBlock</tt>
2448 class</a>
2449</div>
2450
2451<div class="doc_text">
2452
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2453<ul>
Misha Brukmanb0e7e452004-10-29 04:33:19 +0000[diff] [blame]2454
2455<li><tt>BasicBlock(const std::string &amp;Name = "", </tt><tt><a
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2456 href="#Function">Function</a> *Parent = 0)</tt>
Misha Brukmanb0e7e452004-10-29 04:33:19 +0000[diff] [blame]2457
2458<p>The <tt>BasicBlock</tt> constructor is used to create new basic blocks for
2459insertion into a function. The constructor optionally takes a name for the new
2460block, and a <a href="#Function"><tt>Function</tt></a> to insert it into. If
2461the <tt>Parent</tt> parameter is specified, the new <tt>BasicBlock</tt> is
2462automatically inserted at the end of the specified <a
2463href="#Function"><tt>Function</tt></a>, if not specified, the BasicBlock must be
2464manually inserted into the <a href="#Function"><tt>Function</tt></a>.</p></li>
2465
2466<li><tt>BasicBlock::iterator</tt> - Typedef for instruction list iterator<br>
2467<tt>BasicBlock::const_iterator</tt> - Typedef for const_iterator.<br>
2468<tt>begin()</tt>, <tt>end()</tt>, <tt>front()</tt>, <tt>back()</tt>,
Chris Lattner77d69242005-03-15 05:19:20 +0000[diff] [blame]2469<tt>size()</tt>, <tt>empty()</tt>
Misha Brukmanb0e7e452004-10-29 04:33:19 +0000[diff] [blame]2470STL-style functions for accessing the instruction list.
2471
2472<p>These methods and typedefs are forwarding functions that have the same
2473semantics as the standard library methods of the same names. These methods
2474expose the underlying instruction list of a basic block in a way that is easy to
2475manipulate. To get the full complement of container operations (including
2476operations to update the list), you must use the <tt>getInstList()</tt>
2477method.</p></li>
2478
2479<li><tt>BasicBlock::InstListType &amp;getInstList()</tt>
2480
2481<p>This method is used to get access to the underlying container that actually
2482holds the Instructions. This method must be used when there isn't a forwarding
2483function in the <tt>BasicBlock</tt> class for the operation that you would like
2484to perform. Because there are no forwarding functions for "updating"
2485operations, you need to use this if you want to update the contents of a
2486<tt>BasicBlock</tt>.</p></li>
2487
2488<li><tt><a href="#Function">Function</a> *getParent()</tt>
2489
2490<p> Returns a pointer to <a href="#Function"><tt>Function</tt></a> the block is
2491embedded into, or a null pointer if it is homeless.</p></li>
2492
2493<li><tt><a href="#TerminatorInst">TerminatorInst</a> *getTerminator()</tt>
2494
2495<p> Returns a pointer to the terminator instruction that appears at the end of
2496the <tt>BasicBlock</tt>. If there is no terminator instruction, or if the last
2497instruction in the block is not a terminator, then a null pointer is
2498returned.</p></li>
2499
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2500</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2501
2502</div>
2503
2504<!-- ======================================================================= -->
2505<div class="doc_subsection">
2506 <a name="GlobalValue">The <tt>GlobalValue</tt> class</a>
2507</div>
2508
2509<div class="doc_text">
2510
2511<p><tt>#include "<a
2512href="/doxygen/GlobalValue_8h-source.html">llvm/GlobalValue.h</a>"</tt><br>
Misha Brukman384047f2004-06-03 23:29:12 +0000[diff] [blame]2513doxygen info: <a href="/doxygen/classllvm_1_1GlobalValue.html">GlobalValue
2514Class</a><br>
Reid Spencerbe5e85e2006-04-14 14:11:48 +0000[diff] [blame]2515Superclasses: <a href="#Constant"><tt>Constant</tt></a>,
2516<a href="#User"><tt>User</tt></a>, <a href="#Value"><tt>Value</tt></a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2517
2518<p>Global values (<a href="#GlobalVariable"><tt>GlobalVariable</tt></a>s or <a
2519href="#Function"><tt>Function</tt></a>s) are the only LLVM values that are
2520visible in the bodies of all <a href="#Function"><tt>Function</tt></a>s.
2521Because they are visible at global scope, they are also subject to linking with
2522other globals defined in different translation units. To control the linking
2523process, <tt>GlobalValue</tt>s know their linkage rules. Specifically,
2524<tt>GlobalValue</tt>s know whether they have internal or external linkage, as
Reid Spencer8b2da7a2004-07-18 13:10:31 +0000[diff] [blame]2525defined by the <tt>LinkageTypes</tt> enumeration.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2526
2527<p>If a <tt>GlobalValue</tt> has internal linkage (equivalent to being
2528<tt>static</tt> in C), it is not visible to code outside the current translation
2529unit, and does not participate in linking. If it has external linkage, it is
2530visible to external code, and does participate in linking. In addition to
2531linkage information, <tt>GlobalValue</tt>s keep track of which <a
2532href="#Module"><tt>Module</tt></a> they are currently part of.</p>
2533
2534<p>Because <tt>GlobalValue</tt>s are memory objects, they are always referred to
2535by their <b>address</b>. As such, the <a href="#Type"><tt>Type</tt></a> of a
2536global is always a pointer to its contents. It is important to remember this
2537when using the <tt>GetElementPtrInst</tt> instruction because this pointer must
2538be dereferenced first. For example, if you have a <tt>GlobalVariable</tt> (a
2539subclass of <tt>GlobalValue)</tt> that is an array of 24 ints, type <tt>[24 x
Reid Spencer06565dc2007-01-12 17:11:23 +0000[diff] [blame]2540i32]</tt>, then the <tt>GlobalVariable</tt> is a pointer to that array. Although
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2541the address of the first element of this array and the value of the
2542<tt>GlobalVariable</tt> are the same, they have different types. The
Reid Spencer06565dc2007-01-12 17:11:23 +0000[diff] [blame]2543<tt>GlobalVariable</tt>'s type is <tt>[24 x i32]</tt>. The first element's type
2544is <tt>i32.</tt> Because of this, accessing a global value requires you to
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2545dereference the pointer with <tt>GetElementPtrInst</tt> first, then its elements
2546can be accessed. This is explained in the <a href="LangRef.html#globalvars">LLVM
2547Language Reference Manual</a>.</p>
2548
2549</div>
2550
2551<!-- _______________________________________________________________________ -->
2552<div class="doc_subsubsection">
2553 <a name="m_GlobalValue">Important Public Members of the <tt>GlobalValue</tt>
2554 class</a>
2555</div>
2556
2557<div class="doc_text">
2558
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2559<ul>
2560 <li><tt>bool hasInternalLinkage() const</tt><br>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]2561 <tt>bool hasExternalLinkage() const</tt><br>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2562 <tt>void setInternalLinkage(bool HasInternalLinkage)</tt>
2563 <p> These methods manipulate the linkage characteristics of the <tt>GlobalValue</tt>.</p>
2564 <p> </p>
2565 </li>
2566 <li><tt><a href="#Module">Module</a> *getParent()</tt>
2567 <p> This returns the <a href="#Module"><tt>Module</tt></a> that the
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2568GlobalValue is currently embedded into.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2569</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2570
2571</div>
2572
2573<!-- ======================================================================= -->
2574<div class="doc_subsection">
2575 <a name="Function">The <tt>Function</tt> class</a>
2576</div>
2577
2578<div class="doc_text">
2579
2580<p><tt>#include "<a
2581href="/doxygen/Function_8h-source.html">llvm/Function.h</a>"</tt><br> doxygen
Misha Brukman31ca1de2004-06-03 23:35:54 +0000[diff] [blame]2582info: <a href="/doxygen/classllvm_1_1Function.html">Function Class</a><br>
Reid Spencerbe5e85e2006-04-14 14:11:48 +0000[diff] [blame]2583Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>,
2584<a href="#Constant"><tt>Constant</tt></a>,
2585<a href="#User"><tt>User</tt></a>,
2586<a href="#Value"><tt>Value</tt></a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2587
2588<p>The <tt>Function</tt> class represents a single procedure in LLVM. It is
2589actually one of the more complex classes in the LLVM heirarchy because it must
2590keep track of a large amount of data. The <tt>Function</tt> class keeps track
Reid Spencerbe5e85e2006-04-14 14:11:48 +0000[diff] [blame]2591of a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, a list of formal
2592<a href="#Argument"><tt>Argument</tt></a>s, and a
2593<a href="#SymbolTable"><tt>SymbolTable</tt></a>.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2594
2595<p>The list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s is the most
2596commonly used part of <tt>Function</tt> objects. The list imposes an implicit
2597ordering of the blocks in the function, which indicate how the code will be
2598layed out by the backend. Additionally, the first <a
2599href="#BasicBlock"><tt>BasicBlock</tt></a> is the implicit entry node for the
2600<tt>Function</tt>. It is not legal in LLVM to explicitly branch to this initial
2601block. There are no implicit exit nodes, and in fact there may be multiple exit
2602nodes from a single <tt>Function</tt>. If the <a
2603href="#BasicBlock"><tt>BasicBlock</tt></a> list is empty, this indicates that
2604the <tt>Function</tt> is actually a function declaration: the actual body of the
2605function hasn't been linked in yet.</p>
2606
2607<p>In addition to a list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s, the
2608<tt>Function</tt> class also keeps track of the list of formal <a
2609href="#Argument"><tt>Argument</tt></a>s that the function receives. This
2610container manages the lifetime of the <a href="#Argument"><tt>Argument</tt></a>
2611nodes, just like the <a href="#BasicBlock"><tt>BasicBlock</tt></a> list does for
2612the <a href="#BasicBlock"><tt>BasicBlock</tt></a>s.</p>
2613
2614<p>The <a href="#SymbolTable"><tt>SymbolTable</tt></a> is a very rarely used
2615LLVM feature that is only used when you have to look up a value by name. Aside
2616from that, the <a href="#SymbolTable"><tt>SymbolTable</tt></a> is used
2617internally to make sure that there are not conflicts between the names of <a
2618href="#Instruction"><tt>Instruction</tt></a>s, <a
2619href="#BasicBlock"><tt>BasicBlock</tt></a>s, or <a
2620href="#Argument"><tt>Argument</tt></a>s in the function body.</p>
2621
Reid Spencer8b2da7a2004-07-18 13:10:31 +0000[diff] [blame]2622<p>Note that <tt>Function</tt> is a <a href="#GlobalValue">GlobalValue</a>
2623and therefore also a <a href="#Constant">Constant</a>. The value of the function
2624is its address (after linking) which is guaranteed to be constant.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2625</div>
2626
2627<!-- _______________________________________________________________________ -->
2628<div class="doc_subsubsection">
2629 <a name="m_Function">Important Public Members of the <tt>Function</tt>
2630 class</a>
2631</div>
2632
2633<div class="doc_text">
2634
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2635<ul>
2636 <li><tt>Function(const </tt><tt><a href="#FunctionType">FunctionType</a>
Chris Lattnerac479e52004-08-04 05:10:48 +0000[diff] [blame]2637 *Ty, LinkageTypes Linkage, const std::string &amp;N = "", Module* Parent = 0)</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2638
2639 <p>Constructor used when you need to create new <tt>Function</tt>s to add
2640 the the program. The constructor must specify the type of the function to
Chris Lattnerac479e52004-08-04 05:10:48 +0000[diff] [blame]2641 create and what type of linkage the function should have. The <a
2642 href="#FunctionType"><tt>FunctionType</tt></a> argument
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2643 specifies the formal arguments and return value for the function. The same
2644 <a href="#FunctionTypel"><tt>FunctionType</tt></a> value can be used to
2645 create multiple functions. The <tt>Parent</tt> argument specifies the Module
2646 in which the function is defined. If this argument is provided, the function
2647 will automatically be inserted into that module's list of
2648 functions.</p></li>
2649
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2650 <li><tt>bool isExternal()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2651
2652 <p>Return whether or not the <tt>Function</tt> has a body defined. If the
2653 function is "external", it does not have a body, and thus must be resolved
2654 by linking with a function defined in a different translation unit.</p></li>
2655
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2656 <li><tt>Function::iterator</tt> - Typedef for basic block list iterator<br>
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]2657 <tt>Function::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2658
Chris Lattner77d69242005-03-15 05:19:20 +0000[diff] [blame]2659 <tt>begin()</tt>, <tt>end()</tt>
2660 <tt>size()</tt>, <tt>empty()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2661
2662 <p>These are forwarding methods that make it easy to access the contents of
2663 a <tt>Function</tt> object's <a href="#BasicBlock"><tt>BasicBlock</tt></a>
2664 list.</p></li>
2665
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2666 <li><tt>Function::BasicBlockListType &amp;getBasicBlockList()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2667
2668 <p>Returns the list of <a href="#BasicBlock"><tt>BasicBlock</tt></a>s. This
2669 is necessary to use when you need to update the list or perform a complex
2670 action that doesn't have a forwarding method.</p></li>
2671
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]2672 <li><tt>Function::arg_iterator</tt> - Typedef for the argument list
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2673iterator<br>
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]2674 <tt>Function::const_arg_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2675
Chris Lattner77d69242005-03-15 05:19:20 +0000[diff] [blame]2676 <tt>arg_begin()</tt>, <tt>arg_end()</tt>
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]2677 <tt>arg_size()</tt>, <tt>arg_empty()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2678
2679 <p>These are forwarding methods that make it easy to access the contents of
2680 a <tt>Function</tt> object's <a href="#Argument"><tt>Argument</tt></a>
2681 list.</p></li>
2682
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2683 <li><tt>Function::ArgumentListType &amp;getArgumentList()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2684
2685 <p>Returns the list of <a href="#Argument"><tt>Argument</tt></a>s. This is
2686 necessary to use when you need to update the list or perform a complex
2687 action that doesn't have a forwarding method.</p></li>
2688
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2689 <li><tt><a href="#BasicBlock">BasicBlock</a> &amp;getEntryBlock()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2690
2691 <p>Returns the entry <a href="#BasicBlock"><tt>BasicBlock</tt></a> for the
2692 function. Because the entry block for the function is always the first
2693 block, this returns the first block of the <tt>Function</tt>.</p></li>
2694
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2695 <li><tt><a href="#Type">Type</a> *getReturnType()</tt><br>
2696 <tt><a href="#FunctionType">FunctionType</a> *getFunctionType()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2697
2698 <p>This traverses the <a href="#Type"><tt>Type</tt></a> of the
2699 <tt>Function</tt> and returns the return type of the function, or the <a
2700 href="#FunctionType"><tt>FunctionType</tt></a> of the actual
2701 function.</p></li>
2702
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2703 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2704
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2705 <p> Return a pointer to the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2706 for this <tt>Function</tt>.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2707</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2708
2709</div>
2710
2711<!-- ======================================================================= -->
2712<div class="doc_subsection">
2713 <a name="GlobalVariable">The <tt>GlobalVariable</tt> class</a>
2714</div>
2715
2716<div class="doc_text">
2717
2718<p><tt>#include "<a
2719href="/doxygen/GlobalVariable_8h-source.html">llvm/GlobalVariable.h</a>"</tt>
2720<br>
Tanya Lattnera3da7772004-06-22 08:02:25 +0000[diff] [blame]2721doxygen info: <a href="/doxygen/classllvm_1_1GlobalVariable.html">GlobalVariable
Reid Spencerbe5e85e2006-04-14 14:11:48 +0000[diff] [blame]2722 Class</a><br>
2723Superclasses: <a href="#GlobalValue"><tt>GlobalValue</tt></a>,
2724<a href="#Constant"><tt>Constant</tt></a>,
2725<a href="#User"><tt>User</tt></a>,
2726<a href="#Value"><tt>Value</tt></a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2727
2728<p>Global variables are represented with the (suprise suprise)
2729<tt>GlobalVariable</tt> class. Like functions, <tt>GlobalVariable</tt>s are also
2730subclasses of <a href="#GlobalValue"><tt>GlobalValue</tt></a>, and as such are
2731always referenced by their address (global values must live in memory, so their
Reid Spencerbe5e85e2006-04-14 14:11:48 +0000[diff] [blame]2732"name" refers to their constant address). See
2733<a href="#GlobalValue"><tt>GlobalValue</tt></a> for more on this. Global
2734variables may have an initial value (which must be a
2735<a href="#Constant"><tt>Constant</tt></a>), and if they have an initializer,
2736they may be marked as "constant" themselves (indicating that their contents
2737never change at runtime).</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2738</div>
2739
2740<!-- _______________________________________________________________________ -->
2741<div class="doc_subsubsection">
2742 <a name="m_GlobalVariable">Important Public Members of the
2743 <tt>GlobalVariable</tt> class</a>
2744</div>
2745
2746<div class="doc_text">
2747
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2748<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2749 <li><tt>GlobalVariable(const </tt><tt><a href="#Type">Type</a> *Ty, bool
2750 isConstant, LinkageTypes&amp; Linkage, <a href="#Constant">Constant</a>
2751 *Initializer = 0, const std::string &amp;Name = "", Module* Parent = 0)</tt>
2752
2753 <p>Create a new global variable of the specified type. If
2754 <tt>isConstant</tt> is true then the global variable will be marked as
2755 unchanging for the program. The Linkage parameter specifies the type of
2756 linkage (internal, external, weak, linkonce, appending) for the variable. If
2757 the linkage is InternalLinkage, WeakLinkage, or LinkOnceLinkage,&nbsp; then
2758 the resultant global variable will have internal linkage. AppendingLinkage
2759 concatenates together all instances (in different translation units) of the
2760 variable into a single variable but is only applicable to arrays. &nbsp;See
2761 the <a href="LangRef.html#modulestructure">LLVM Language Reference</a> for
2762 further details on linkage types. Optionally an initializer, a name, and the
2763 module to put the variable into may be specified for the global variable as
2764 well.</p></li>
2765
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2766 <li><tt>bool isConstant() const</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2767
2768 <p>Returns true if this is a global variable that is known not to
2769 be modified at runtime.</p></li>
2770
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2771 <li><tt>bool hasInitializer()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2772
2773 <p>Returns true if this <tt>GlobalVariable</tt> has an intializer.</p></li>
2774
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2775 <li><tt><a href="#Constant">Constant</a> *getInitializer()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2776
2777 <p>Returns the intial value for a <tt>GlobalVariable</tt>. It is not legal
2778 to call this method if there is no initializer.</p></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2779</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2780
2781</div>
2782
2783<!-- ======================================================================= -->
2784<div class="doc_subsection">
2785 <a name="Module">The <tt>Module</tt> class</a>
2786</div>
2787
2788<div class="doc_text">
2789
2790<p><tt>#include "<a
2791href="/doxygen/Module_8h-source.html">llvm/Module.h</a>"</tt><br> doxygen info:
Tanya Lattnera3da7772004-06-22 08:02:25 +0000[diff] [blame]2792<a href="/doxygen/classllvm_1_1Module.html">Module Class</a></p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2793
2794<p>The <tt>Module</tt> class represents the top level structure present in LLVM
2795programs. An LLVM module is effectively either a translation unit of the
2796original program or a combination of several translation units merged by the
2797linker. The <tt>Module</tt> class keeps track of a list of <a
2798href="#Function"><tt>Function</tt></a>s, a list of <a
2799href="#GlobalVariable"><tt>GlobalVariable</tt></a>s, and a <a
2800href="#SymbolTable"><tt>SymbolTable</tt></a>. Additionally, it contains a few
2801helpful member functions that try to make common operations easy.</p>
2802
2803</div>
2804
2805<!-- _______________________________________________________________________ -->
2806<div class="doc_subsubsection">
2807 <a name="m_Module">Important Public Members of the <tt>Module</tt> class</a>
2808</div>
2809
2810<div class="doc_text">
2811
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2812<ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2813 <li><tt>Module::Module(std::string name = "")</tt></li>
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2814</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2815
2816<p>Constructing a <a href="#Module">Module</a> is easy. You can optionally
2817provide a name for it (probably based on the name of the translation unit).</p>
2818
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2819<ul>
2820 <li><tt>Module::iterator</tt> - Typedef for function list iterator<br>
Chris Lattner0377de42002-09-06 14:50:55 +0000[diff] [blame]2821 <tt>Module::const_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2822
Chris Lattner77d69242005-03-15 05:19:20 +0000[diff] [blame]2823 <tt>begin()</tt>, <tt>end()</tt>
2824 <tt>size()</tt>, <tt>empty()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2825
2826 <p>These are forwarding methods that make it easy to access the contents of
2827 a <tt>Module</tt> object's <a href="#Function"><tt>Function</tt></a>
2828 list.</p></li>
2829
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2830 <li><tt>Module::FunctionListType &amp;getFunctionList()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2831
2832 <p> Returns the list of <a href="#Function"><tt>Function</tt></a>s. This is
2833 necessary to use when you need to update the list or perform a complex
2834 action that doesn't have a forwarding method.</p>
2835
2836 <p><!-- Global Variable --></p></li>
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]2837</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2838
2839<hr>
2840
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]2841<ul>
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]2842 <li><tt>Module::global_iterator</tt> - Typedef for global variable list iterator<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2843
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]2844 <tt>Module::const_global_iterator</tt> - Typedef for const_iterator.<br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2845
Chris Lattner77d69242005-03-15 05:19:20 +0000[diff] [blame]2846 <tt>global_begin()</tt>, <tt>global_end()</tt>
Chris Lattner89cc2652005-03-15 04:48:32 +0000[diff] [blame]2847 <tt>global_size()</tt>, <tt>global_empty()</tt>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2848
2849 <p> These are forwarding methods that make it easy to access the contents of
2850 a <tt>Module</tt> object's <a
2851 href="#GlobalVariable"><tt>GlobalVariable</tt></a> list.</p></li>
2852
2853 <li><tt>Module::GlobalListType &amp;getGlobalList()</tt>
2854
2855 <p>Returns the list of <a
2856 href="#GlobalVariable"><tt>GlobalVariable</tt></a>s. This is necessary to
2857 use when you need to update the list or perform a complex action that
2858 doesn't have a forwarding method.</p>
2859
2860 <p><!-- Symbol table stuff --> </p></li>
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]2861</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2862
2863<hr>
2864
2865<ul>
2866 <li><tt><a href="#SymbolTable">SymbolTable</a> *getSymbolTable()</tt>
2867
2868 <p>Return a reference to the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
2869 for this <tt>Module</tt>.</p>
2870
2871 <p><!-- Convenience methods --></p></li>
2872</ul>
2873
2874<hr>
2875
2876<ul>
2877 <li><tt><a href="#Function">Function</a> *getFunction(const std::string
2878 &amp;Name, const <a href="#FunctionType">FunctionType</a> *Ty)</tt>
2879
2880 <p>Look up the specified function in the <tt>Module</tt> <a
2881 href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, return
2882 <tt>null</tt>.</p></li>
2883
2884 <li><tt><a href="#Function">Function</a> *getOrInsertFunction(const
2885 std::string &amp;Name, const <a href="#FunctionType">FunctionType</a> *T)</tt>
2886
2887 <p>Look up the specified function in the <tt>Module</tt> <a
2888 href="#SymbolTable"><tt>SymbolTable</tt></a>. If it does not exist, add an
2889 external declaration for the function and return it.</p></li>
2890
2891 <li><tt>std::string getTypeName(const <a href="#Type">Type</a> *Ty)</tt>
2892
2893 <p>If there is at least one entry in the <a
2894 href="#SymbolTable"><tt>SymbolTable</tt></a> for the specified <a
2895 href="#Type"><tt>Type</tt></a>, return it. Otherwise return the empty
2896 string.</p></li>
2897
2898 <li><tt>bool addTypeName(const std::string &amp;Name, const <a
2899 href="#Type">Type</a> *Ty)</tt>
2900
2901 <p>Insert an entry in the <a href="#SymbolTable"><tt>SymbolTable</tt></a>
2902 mapping <tt>Name</tt> to <tt>Ty</tt>. If there is already an entry for this
2903 name, true is returned and the <a
2904 href="#SymbolTable"><tt>SymbolTable</tt></a> is not modified.</p></li>
2905</ul>
2906
2907</div>
2908
2909<!-- ======================================================================= -->
2910<div class="doc_subsection">
2911 <a name="Constant">The <tt>Constant</tt> class and subclasses</a>
2912</div>
2913
2914<div class="doc_text">
2915
2916<p>Constant represents a base class for different types of constants. It
Reid Spencer53bfebc2007-01-12 03:36:33 +0000[diff] [blame]2917is subclassed by ConstantInt, ConstantArray, etc. for representing
Reid Spencerb83eb642006-10-20 07:07:24 +0000[diff] [blame]2918the various types of Constants.</p>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2919
2920</div>
2921
2922<!-- _______________________________________________________________________ -->
2923<div class="doc_subsubsection">
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]2924 <a name="m_Constant">Important Public Methods</a>
2925</div>
2926<div class="doc_text">
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2927</div>
2928
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]2929<!-- _______________________________________________________________________ -->
2930<div class="doc_subsubsection">Important Subclasses of Constant </div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2931<div class="doc_text">
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]2932<ul>
Reid Spencer53bfebc2007-01-12 03:36:33 +0000[diff] [blame]2933 <li>ConstantInt : This subclass of Constant represents an integer constant of
2934 any width, including boolean (1 bit integer).
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2935 <ul>
Reid Spencerb83eb642006-10-20 07:07:24 +0000[diff] [blame]2936 <li><tt>int64_t getSExtValue() const</tt>: Returns the underlying value of
2937 this constant as a sign extended signed integer value.</li>
2938 <li><tt>uint64_t getZExtValue() const</tt>: Returns the underlying value
2939 of this constant as a zero extended unsigned integer value.</li>
Reid Spencer53bfebc2007-01-12 03:36:33 +0000[diff] [blame]2940 <li><tt>static ConstantInt* get(const Type *Ty, uint64_t Val)</tt>:
2941 Returns the ConstantInt object that represents the value provided by
2942 <tt>Val</tt> for integer type <tt>Ty</tt>.</li>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]2943 </ul>
2944 </li>
2945 <li>ConstantFP : This class represents a floating point constant.
2946 <ul>
2947 <li><tt>double getValue() const</tt>: Returns the underlying value of
2948 this constant. </li>
2949 </ul>
2950 </li>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]2951 <li>ConstantArray : This represents a constant array.
2952 <ul>
2953 <li><tt>const std::vector&lt;Use&gt; &amp;getValues() const</tt>: Returns
Chris Lattner58360822005-01-17 00:12:04 +0000[diff] [blame]2954 a vector of component constants that makeup this array. </li>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]2955 </ul>
2956 </li>
2957 <li>ConstantStruct : This represents a constant struct.
2958 <ul>
2959 <li><tt>const std::vector&lt;Use&gt; &amp;getValues() const</tt>: Returns
Chris Lattner58360822005-01-17 00:12:04 +0000[diff] [blame]2960 a vector of component constants that makeup this array. </li>
Reid Spencerfe8f4ff2004-11-01 09:02:53 +0000[diff] [blame]2961 </ul>
2962 </li>
2963 <li>GlobalValue : This represents either a global variable or a function. In
2964 either case, the value is a constant fixed address (after linking).
2965 </li>
Chris Lattnerc75ff9a2002-10-01 23:17:09 +0000[diff] [blame]2966</ul>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2967</div>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2968<!-- ======================================================================= -->
2969<div class="doc_subsection">
2970 <a name="Argument">The <tt>Argument</tt> class</a>
2971</div>
2972
2973<div class="doc_text">
2974
2975<p>This subclass of Value defines the interface for incoming formal
Chris Lattner58360822005-01-17 00:12:04 +0000[diff] [blame]2976arguments to a function. A Function maintains a list of its formal
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2977arguments. An argument has a pointer to the parent Function.</p>
2978
2979</div>
2980
Chris Lattner9355b472002-09-06 02:50:58 +0000[diff] [blame]2981<!-- *********************************************************************** -->
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2982<hr>
2983<address>
2984 <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
2985 src="http://jigsaw.w3.org/css-validator/images/vcss" alt="Valid CSS!"></a>
2986 <a href="http://validator.w3.org/check/referer"><img
2987 src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01!" /></a>
2988
2989 <a href="mailto:dhurjati@cs.uiuc.edu">Dinakar Dhurjati</a> and
2990 <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
Reid Spencer05fe4b02006-03-14 05:39:39 +0000[diff] [blame]2991 <a href="http://llvm.org">The LLVM Compiler Infrastructure</a><br>
Misha Brukman13fd15c2004-01-15 00:14:41 +0000[diff] [blame]2992 Last modified: $Date$
2993</address>
2994
Chris Lattner261efe92003-11-25 01:02:51 +0000[diff] [blame]2995</body>
2996</html>